Equipment Specifications.docx

7/27/2019 Equipment Specifications.docx

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Equipment Specifications, Calibration, and Care

Basic instrumentation for a GPS network survey includes multiple setsofreceivers, antennas, fixed-height tripods, and meteorological instruments. Identicalequipment should be used whenever possible to minimize the effect of equipment biases.The compatibility of mixing different instrument models or brands should be demonstrated byperforming a validation survey.

Survey equipment, like all scientific instrumentation, should be handled with care,maintained according to manufacturer specifications, and calibrated on a regular basis.Equipment calibrations should be performed at the start and end of a project, before andafter any maintenance, and at sufficient intervals to maintain data integrity. Any data not

bracketed by successful calibrations are suspect. To prevent the invalidation of good data,frequent calibrations are recommended. The entire system of GPS equipment, personnel,and processing procedures should be proven with a validation survey as a final check toensure all components interact properly.

The following equipment is described below:

1. ReceiverSpecifications2. Antenna Specifications3. Tripod Specifications4. Tribrach Specifications5. Meteorological Equipment Specifications

6. Personnel Specifications

A-1. Receiver Specifications:[receiver

operation][top] [home]

The receivers used for network surveys should record the fullwavelength carrier phase and signal strength of both the L1 and L2frequencies, and track at least eight satellites simultaneously onparallel channels. Dual frequency instruments are recommended forall baselines longer than 10 km.

ient memory and

battery power for the entire field campaign.test reports are available from the Federal Geodetic Control Subcommittee

(FGCS).

Receiver Calibration and Care:

Ensure that your receiver contains the latest manufacturer's firmware upgrades. A zero-baseline test can measure receiver internal noise if the performance is suspect. Consultyour user's manual for additional specifications.

A-2. Antenna Specifications:[antenna height

measurement][top] [home]
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#validationhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#validationhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.fgdc.gov/participation/working-groups-subcommittees/fgcs/instruments/reports/http://www.fgdc.gov/participation/working-groups-subcommittees/fgcs/http://www.cfm.ohio-state.edu/research/webreceivers/zero_baseline.htmhttp://www.cfm.ohio-state.edu/research/webreceivers/zero_baseline.htmhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.cfm.ohio-state.edu/research/webreceivers/zero_baseline.htmhttp://www.cfm.ohio-state.edu/research/webreceivers/zero_baseline.htmhttp://www.fgdc.gov/participation/working-groups-subcommittees/fgcs/http://www.fgdc.gov/participation/working-groups-subcommittees/fgcs/instruments/reports/http://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#validationhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#validationhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiver


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The antennas should have stable phase centers and choke rings or large (>16 cm) ground planes to minimize multipath interference, and a commonorientation indicator (e.g., an arrow) to point north during observations.

Antenna Calibration and Care:

All antenna models used shall have undergone Antenna Calibration by the NationalGeodetic Survey (NGS). Consult your user's manual for other specifications.

A-3. Tripod Specifications: [tripod setup] [top] [home]

The tripods used must facilitate precise offset measurements between the mark datum pointand the Antenna Reference Point (ARP). Fixed height tripods are preferable, due to thedecreased potential for antenna centering and height measurement errors.

Tripod Calibration and Care:

stability with each use. Ensure that hinges, clamps, andfeet are secure and in good repair.

-height tripods shall be tested for stability, plumb alignment, andheight verification at the start and end of each project.

Link - SECO GPS Tripod Length Test

A-4. Tribrach Specifications:

Tribrachs used shall be of suitable quality and condition for high-accuracy surveys. Consultwith your Project Coordinator for details.

Tribrach Calibration and Care:

The optical plummet alignment shall be tested at the start and end of each project.

Link - Using SECO Tribrach Adjusters

Meteorological equipment includes a psychrometer (wet-bulb and dry-bulbthermometers) to measure temperatures and a barometer or altimeter to measure

A-5. Meteorological Equipment Specifications:[weather

observations][top] [home]
http://www.ngs.noaa.gov/ANTCAL/http://www.ngs.noaa.gov/http://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.surveying.com/tech_tips/details.asp?techTipNo=4http://www.surveying.com/tech_tips/details.asp?techTipNo=12http://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.surveying.com/tech_tips/details.asp?techTipNo=12http://www.surveying.com/tech_tips/details.asp?techTipNo=4http://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tripodhttp://www.ngs.noaa.gov/http://www.ngs.noaa.gov/ANTCAL/


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atmospheric pressure. Relative humidity can either be measured with a hygrometer orcomputed (the preferred method) from psychrometer and barometer readings.

Meteorological Equipment Calibration and Care:

Meteorological equipment should be calibrated at the beginning and end of a project. Usethe Meteorological Equipment Comparison Form to compare your instruments with standardinstruments, available at National Weather Service offices.

A-6. Personnel Specifications: ]

All field personnel should be trained in the avoidance of systematic errors and blunders

during field operations. Field personnel often work alone and must be prepared to make

wise, on-the-spot decisions regarding mark identification and stability, equipment use and

troubleshooting, and antenna setup. Office personnel should be familiar with geodetic

concepts and least-squares adjustments.

PLANNING

A-1. Reconnaissance Surveys:

Proper field reconnaissance is a prerequisite for any control survey.Reconnaissance should include a review of existing control networks, mark

recovery and maintenance, station selection, setting of new monuments as

necessary, and compilation ofupdated station descriptions into standard

FGCS bluebookformat.

See the NGS ANA website for helpful information about reconnaissance, stationselection, marksetting, etc.

A-2. High Accuracy Reference Network (HARN) Surveys: [top] [home]

High Accuracy Reference Networks (HARNs)are statewide GPS survey networks which formthe highest order of monumented control for the

National Spatial Reference System (NSRS).Comprised of an NGS-maintained Federal Base

Network(FBN) at 100 km station spacing and avolunteer-densified Cooperative Base Network

(CBN) at 25-50 km spacing, HARN stations serve as control for regional and local

surveys. Contemporary HARN surveys are conducted in accordance with the

following specifications:
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#wxchkloghttp://www.nws.noaa.gov/organization.phphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#recoveryhttp://www.ngs.noaa.gov/FGCS/BlueBook/http://www.ngs.noaa.gov/AERO/Supinst.htmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/faq.shtml#WhatHARNhttp://www.ngs.noaa.gov/PUBS_LIB/develop_NSRS.htmlhttp://www.ngs.noaa.gov/PROJECTS/FBN/http://www.ngs.noaa.gov/PROJECTS/FBN/http://www.ngs.noaa.gov/PUBS_LIB/develop_NSRS.htmlhttp://www.ngs.noaa.gov/faq.shtml#WhatHARNhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/AERO/Supinst.htmlhttp://www.ngs.noaa.gov/FGCS/BlueBook/http://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#recoveryhttp://www.nws.noaa.gov/organization.phphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#wxchklog


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Station Requirements:

HARN Stations: The survey shall include FBN stations established at 100 kmnominal spacing and additional CBN stations if desired. Refer to "FBN Station

Selection Guidelines" for HARN monumentation and siting criteria.

Hub Stations: The survey shall include at least 1 hub station located within 300km of each HARN station. Hub stations should include all Continuously Operating

Reference Stations (CORS) in the project area, and any HARN or bench markstations located in secure areas.

Bench Marks: The survey shall include at least 1 each, first- or second-order,stability class -A or class-B bench mark located within 200 km of each HARN

station.

Observation Requirements:

HARN Stations: All HARN stations shall be observed in at least 3 sessions on 3different days. Each observation shall be continuous for at least 5 hours, and

simultaneous with all other stations in the observing session. At least 1 of the 3sessions shall be observed under a unique satellite configuration, offset 4 or moresidereal hours from other observations. Session times shall be selected to minimize

Positional Dilution of Precision (PDOP) throughout the observation.

Each HARN station shall be co-observed with a hub station and adjacent stations.

At least half of the station pair (baseline) observations shall be repeated. Data shallbe recorded at 15 second epochs and 10 degree elevation masks.

Hub Stations: Each hub station shall be observed with the nearest National CORSstation for 1 session of at least 72 continuous hours with 30 second epochs.

These guidelines for HARN surveys are summarized in Table 4.1 below:

Table 4.1 Network Design Guidelines for HARN Surveys

Minimum Number of Stations All National CORS in or near the project area

Maximum Station Spacing

Between HARN stations < 100 km (nominal

spacing)

Between HARN and hub stations < 300 km

Between HARN and bench mark < 200 km

Required Baselines

For HARN stations:

To a hub station in each session

To adjacent stations

Repeat at least 50% of all baselines

For hub stations:

To the nearest National CORS
http://www.ngs.noaa.gov/PROJECTS/INSTRUCTIONS/FBN/FBN_Station_Selection_Guidelines.pdfhttp://www.ngs.noaa.gov/PROJECTS/INSTRUCTIONS/FBN/FBN_Station_Selection_Guidelines.pdfhttp://www.ngs.noaa.gov/CORS/http://www.ngs.noaa.gov/CORS/http://www.ngs.noaa.gov/PROJECTS/INSTRUCTIONS/FBN/FBN_Station_Selection_Guidelines.pdfhttp://www.ngs.noaa.gov/PROJECTS/INSTRUCTIONS/FBN/FBN_Station_Selection_Guidelines.pdf


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Observations per Baseline

For HARN stations:

3 each, 5 hour observations on 3 differentdays

For hub stations:

1 each, 72 hour observation, 30 second epochs

Sidereal Time Offset Between Repeated

Observations

Repeated observations are conducted on different

days

At least 1 observation shall be offset by 4 hours

Fixed-height Tripods Required?Required for all FBN stations hub stations and

bench marks

Acquire Meteorological Data?At all stations at the beginning, middle, and end

of each observation

Data Acquisition Parameters 15 second epochs, 10 degree elevation masks

Data Processing Parameters30 second epochs, 15 degree elevation masks,

precise ephemerides

A-3. User Densification Network (UDN) Surveys: [top] [home]

User Densification Network (UDN)surveys allow regional densification

of the HARN networks. UDN

surveys are conducted in accordance

with the following specifications:


UDN Stations: The survey shall

include UDN stations established at 25 km spacing or less.

HARN Stations: The survey shall include at least 2 HARN stations.


UDN Stations: Each UDN station shall be observed in at least two 30 minutesessions. Each UDN station shall be co-observed with adjacent stations. Data shall

be recorded at 15 second epochs and 10 degree elevation masks.

These guidelines for UDN surveys are summarized in Table 4.2 below:

Table 4.2 Network Design Guidelines for UDN Surveys

Minimum Number of Stations At least 2 HARN stations

Maximum Station Spacing < 25 km between UDN stations

Required Baselines To adjacent stations

Observations per Baseline 2 each, 30 minute observations
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#top


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Sidereal Time Offset Between

Repeated ObservationsNo time offset required

Fixed-height Tripods Required? No fixed-height tripods required

Acquire Meteorological Data? At representative stations in the middle of eachobservation

Data Acquisition Parameters 30 second epochs, 15 degree elevation masks

Data Processing Parameters30 second epochs, 15 degree elevation masks,

precise or rapid ephemerides

A-4. GPS Orthometric Height Surveys: [top] [home]

NOTE: For published GPS OrthometricHeight survey requirements, see NOAA

Technical Memorandum NOS-NGS-58;"Guidelines for Establishing GPS-

derived Ellipsoid Heights".

Recent studies have shown that withsufficient orthometric height control,

high accuracy vertical control projectscan be efficiently performed using GPS. Orthometric height surveys are conducted

in accordance with the following specifications:


Local Stations: The height stations established in this survey are referred to as

local stations. See Table 4.3 for maximum station spacings.

Control Stations: The survey shall include 3 or more primary control stationsdistributed throughout the project area. All control stations shall be National CORSor vertical first-order, stability class-A or class-B HARN stations.

Hub Stations: The survey shall include 3 or more subordinate control stations,

called hub stations, distributed throughout the project and located within 75 kmfrom the control stations. See Table 4.3 for maximum station spacings. Although

hub stations can be newly established in this project, the use of existing HARNstations and stable bench marks is preferred.

Bench marks: The survey shall include at least 4 each, vertical first-order,stability class-A or class-B bench marks spaced less than 20 km apart and

distributed both horizontally and vertically throughout the project area. Use

additional bench marks whenever practical.
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PUBS_LIB/NGS-58.htmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#top


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Local Stations: All local stations shall be connected to the 2 nearest adjacentstations of any type by observing for 30 minutes on each of 2 or more days, at

different times of day, and shall be connected to 2 hub or control stations byindependent paths. For these observations, please note the following exceptions:

For baselines longer than 10 km, increase the 30 minute observations to 1 hour.

For baselines longer than 15 km, increase the 30 minute observations to 2 hours.For the 2 cm horizontal, 5 cm orthometric height local accuracy level, there is nominimum time requirement. The baselines shall be observed long enough to ensure

that all integers are fixed and the Root Mean Square Error (RMSE) for the baseline

solution does not exceed 1.5 cm.

Hub Stations: Each hub station shall be directly connected to the nearest controlstation and 2 other hub stations, and shall be connected to a second control station

by an independent path. Each of these baselines shall be observed for 5 hours oneach of 3 or more days. Hub stations shall be connected to the 2 nearest hub

stations, and the 2 nearest adjacent stations of any type, by observing for at least 30

minutes on each of 2 or more days, at different times of day.

Independence of Observations:

In an attempt to provide independent atmospheric, satellite, and tidal conditions,

subsequent observations of all repeated baselines shall occur on different days,with as long a time interval between observations as is practical. Because the GPSsatellite geometry repeats every 12 hours*, an additional time shift of 3 to 9hours is required to observe unique satellite constellations. Refer to the following

table for examples:

First

Session

Repeated Session (a.m. or

p.m.)

First

Session

Repeated Session (a.m. or

p.m.)

Began at 1 Observe between 4 and 10 Began at 7 Observe between 10 and 4






* Note that the actual orbit period is approximately 11 hours and 58 minutes,precessing 4 minutes per day. For repeated baselines observed more than 1 week


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apart, this daily 4 minute change should be taken into account when scheduling the

repeated sessions to meet the satellite geometry requirement.

These guidelines for GPS orthometric height surveys are summarized in Table 4.3

below:

Table 4.3 Network Design Guidelines for GPS Orthometric Height Surveys

Station

Type:Control Stations Hub Stations Local Stations

Local

Accuracy:

1 cm

Horizontal2 cm

Orthometri

c

2 cm

Horizontal5 cm

Orthometri

c

1 cm

Horizontal2 cm

Orthometri

c

2 cm

Horizontal5 cm

Orthometri

c

1 cm

Horizontal2 cm

Orthometri

c

2 cm

Horizontal5 cm

Orthometri

c

Min. #

stations

3 or more control

stations3 or more hub stations No minimum number

Max.

Station

Spacing

Between control and hub

stations

75 km spacing

40 km

spacing

50 km

spacing

10 km

spacing

average 7

km

20 km

spacing

average 10

km

Required

Baseline

Ties

Control stations must be

CORS

or existing A-or B- order

NSRS stations with 3-D

ITRF coordinates

5 hour observations: To

nearest control, 2 other

hub stations, and

independent path to

second control

30 minute obs: To 2

nearest hub stations and

2 nearest adjacent

stations.

Independent paths to 2hub or control stations;

To 2 nearest adjacent

stations.

Observation

s per Base

line

5 hour observations on 3

days

5 hour observations on 3

days

30 minute observations

on 2 days

30 minute

obs

on 2 days

No

minimum

time obs.

on 2 days

Sidereal

Time

Between

Obs.

Repeat observations on

different

days 3 to 9 hours


different

days 3 to 9 hours


different

days 3 to 9 hours

Fixed

Height

Tripod Rqd.

Yes Yes No Yes No

Acquire

Met. Data

At the beginning middle

and end of session

At the beginning and

end of sessionNo

Data Acq. 15 seconds 10 degrees 15 seconds 10 degrees 15 sec 10 5 sec 10


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Parameters VDOP < 6 for 90% of

session

VDOP < 6 for 90% of

session

degrees

VDOP


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B-2. Tripod Setup:[tripod

specifications] [top] [home]

Fixed height tripods are preferred over slip-leg tripods, as they reduce the potential

forantenna height measurement errors. If a slip-leg tripod is used, a low tripodsetup is preferred to minimize eccentricities, though the antenna should be set highenough to avoid obstructions. Eccentric setups (antenna out of plumb from thestation datum point) are to be avoided. Note any eccentricities on the observation

log.

Tripod legs should be well set and weighted with sandbags, chain, or spikes tominimize movement.

Plumbing bubbles must be shaded for at least 3 minutes before use to minimize

convective currents in the bubble fluid. On tripods with rotating center poles, thebubble must be rotated and checked level throughout a 180-degree arc.

Antennas should be oriented towards true north, as closely as can be accomplished

with a hand compass. Note the magnetic declination in your local area to convert

from magnetic north to true north.

If possible, take a photograph of the tripod setup with a close-up of the antenna as

viewed from the side. This photograph may be useful in identifying any variations

in antenna configuration (type of radome or ground plane used.)

Link - Setup Instructions for SECO Precise GPS Antenna Tripods

B-3. Antenna Height Measurement:[antenna

http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#troublehttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngdc.noaa.gov/geomagmodels/Declination.jsphttp://www.surveying.com/tech_tips/details.asp?techTipNo=13http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.surveying.com/tech_tips/details.asp?techTipNo=13http://www.ngdc.noaa.gov/geomagmodels/Declination.jsphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#troublehttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tripod


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The proper

recordation of

antenna height

is critical. TheAntenna Height

used at NGS is

the vertical

distance

between the

station datum

point and the

Antenna

Reference Point

(ARP). Observe

rs mustcarefully

measure and

check this

height, and

record and

describe all

measurements

and antenna

constants.

Record all

values to

0.0001 meters

or 0.001 foot.

All

measurement

computations

must be

checked and

initialed by

another person.

ixed-height

tripods simplify the measurement of antenna height (H). The calibrated tripodheight (A) should be checked with a quick measurement. Ensure that the antenna mates

securely with the tripod head, and that any gap (B)between the tripod head and ARP is

measured and included. The antenna height can then be computed from the following

equation:

Antenna Height H= (A + B)


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NOTE: Leica brand antennas use a measuring hook to determine the vertical distance

between the mark and antenna. Record the measured distance from the mark to the hook as

"a", and the offset from the hook to the ARP as "b".

Slip-leg tripods antenna height (H) is usually measured by slant-height(S), thedistance of the hypotenuse from the station datum point to the bottom edge of the antenna

ground plane (BGP). Measure the slant height to at least 3 points around the antenna; these

measurements should all agree to within 1 millimeter or the antenna should be replumbed.

Independent measurements of the antenna height above the mark in both metric and Imperial

units must be made before and after each session. From the antenna specification sheet in

your user's manual, determine the radius (R) of the ground plane and the offset

constant (C)between the BGP and the ARP. The antenna height can then be computed from

the following Pythagorean equation:

Antenna Height H= ( sqrt(S2 - R2) - C)

Compare Metric and Imperial measurements using the following equations:

Meters = Feet (0.3048) Example: 1.286 Meters = 4.219 Feet

Feet = Meters (0.3048) Example: 5.345 Feet = 1.629 Meters

Note that the 3-dimensional datum point of a standard survey disk is located at or above the

dimple in the disk's center, on a level with the highest point of the disk, where the foot of a

level rod would rest. If the point of the fixed-height pole or slant-height measuring rod

intrudes significantly below this level to reach the bottom of the dimple (1 millimeter or

more), make a careful measurement of the vertical separation and note this on the observation

log.

B-4. Tribrach Operation:[tribrach


See your user's manual for operational details.

Link - SECO Tips-Setting Up the GPS Optical Plummet

B-5. Weather Observations:[meteorology

equipment

specifications]

[top] [home]

Measure and record weather data (temperature, pressure, relative humidity, andweather codes) at the beginning, middle, and end of each observing session, and at

sufficient intervals during weather events (storm fronts, wind, snow, or rain, etc.)to describe all conditions observed. For accurate readings, acclimate the weather

equipment for approximately 10 minutes prior to use. Note that even though these

meteorological data may not all be used during vectorprocessing, they may be

helpful during the analysis of results and in future reprocessing with more robustsoftware.
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.surveying.com/tech_tips/details.asp?techTipNo=21http://www.surveying.com/tech_tips/details.asp?techTipNo=21http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#processhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#processhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.surveying.com/tech_tips/details.asp?techTipNo=21http://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrachhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#tribrach


13/15

The measurements must be made in the vicinity of the GPS antenna, taking care

not to obstruct the GPS signals. Indicate on the observation log the time and

location of the meteorological observations. At stations in the vicinity of airports(within 5 km and at approximately same elevation), weather data from the airport

(available on the Interactive Weather Information Network) may be substituted foractual measurements, if no portable meteorological instruments are available.

Temperature: Read and record the dry-bulb and wet-bulb temperatures to the nearest degreeCelsius.

Conversion: C = /9 (F-32) Example: 76oF = 24.4 C

Pressure: Read and record the absolute or station pressure (NOT corrected for sea level) tothe nearest millibar.

Conversion: mbar = ( n g/0.75 ) * 25.4 Example: 29.98 in Hg = 1015.32 mbar

Relative Humidity: Compute the relative humidity from temperature and pressurereadings using NGS program RELHUM or the NWS Weather Calculator.Electronic hygrometers are acceptable as long as the equipment is calibrated andall calibration documentation and offsets are furnished to the Project Coordinator.

Weather Codes: A 5-digit code is used to summarize the general weather

conditions, as described below:

WEATHER CODE 0 1 2

PROBLEM

(0 or

1)

0.... = No problem

encountered

1.... = Problem

encountered 2.... = Not used

VISIBILITY(0, 1,

or 2)

.0... = Good (over 15

miles)

.1... = Fair (7 to 15

miles)

.2... = Poor

(under 7 miles)

TEMPERATURE(0, 1,

or 2)

..0.. = Normal (32oF

to 80oF)

..1.. = Hot (over

80oF)

..2.. = Cold

(under 32oF)

CLOUD COVER(0, 1,

or 2)

...0. = Clear (under

20%)

...1. = Cloudy (20%

to 70%)

...2. = Overcast

(over 70%)

WIND(0, 1,

or 2)

....0 = Calm (under 5

mph)

....1 = Moderate (5

to 15 mph)

....2 = Strong

(over 15 mph)

Examples:

Code

00000 =

0.... (=No

problems),

.0... (=good

visibility),

..0.. (=normal

temperature),

...0. (=clear

sky),

....0 (=calm

wind)

= Code

00000

Code

12121 =

1....

(=Problems),

.2... (=poor

visibility),

..1.. (=hot

temperature),

...2.

(=overcast),

....1

(=moderate

wind)

= Code

12121

B-6. Personnel Operation: [personnelspecifications]

[top] [home]
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.nws.noaa.gov/view/largemap.phphttp://www.srh.noaa.gov/epz/?n=wxcalchttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#personnelhttp://www.srh.noaa.gov/epz/?n=wxcalchttp://www.nws.noaa.gov/view/largemap.phphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obslog


14/15

Survey operations shall be conducted with due regard to the safety of personnel

and equipment. Contact with the airport traffic control tower is mandatory during

surveys at any controlled airports.

C. Observer Checklist:.

[equipment

checklist] [top] [home]

____Determine the scheduled start day and time for the session. Note the UTC-to-local time

difference (e.g., UTC to Pacific Daylight is - 7 hours).

____Assemble all items from the Equipment Checklist. Ensure all equipment is in good

repair and within calibration limits.

____ Arrive at the station about 1 hour prior to the scheduled start time.

____Park your vehicle in a safe manner. Avoid hindering the equipment setup or creatingmultipath signals near the GPS antenna.

____Obtain a station rubbing or sketch on a Pencil Rubbing Form. Compare the station

stamping with the Station Description.

____Set the tripod and GPS antenna plumb over the station.

____ Place sandbags, chain, or spikes at all tripod feet.

____ Align the antenna orientation indicator (arrow) to True North.

____ Attach the GPS receiverto the antenna and batteries, confirming all connections.

____ Ensure that the antenna setup is stable and that the antenna is plumb over the station.

____Measure the antenna height in meters and feet, and record your measurements in the

"Before" column of the NGS Observation Log

____ Reconfirm that the antenna is plumb.

____ Check GPS receiver available memory, power supply, and data logging parameters

____ Begin the session no more than 10 minutes prior to the scheduled start time.

____ Confirm that the GPS receiver is actually recording data.

____ If possible, input the following into the GPS digital data file:

Change filename to standard NGS filename

Enter antenna type and antenna height

Do NOT record weather data, event markers, or survey notes in the digital data

____ Monitor the receiver (logging), antenna setup (plumb), and battery health (good).

____ Consult the Troubleshooting Guide if you encounter problems.

____ Acclimate the meteorology equipment; measure and record weather observations.

____ Fill-in the NGS Observation Log with all pertinent data.

____Check the provided Visibility Obstruction Diagram and the Station Datasheet

orStation Description; note any changes.

____Photograph the station mark, antenna setup, to-reach view, and visibility obstructions

with a digital camera.

____

Acclimate the meteorology equipment; measure and record weather observations at the

session midpoint.
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://ww2010.atmos.uiuc.edu/(Gl)/guides/maps/utc/frutc.rxmlhttp://ww2010.atmos.uiuc.edu/(Gl)/guides/maps/utc/frutc.rxmlhttp://ww2010.atmos.uiuc.edu/(Gl)/guides/maps/utc/frutc.rxmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#specshttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#formathttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#troublehttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#visibilityhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#datasheethttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#recoveryhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#recoveryhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#datasheethttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#visibilityhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#wxgearhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#troublehttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#formathttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#receiverhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tripodhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#antennahttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#specshttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://ww2010.atmos.uiuc.edu/(Gl)/guides/maps/utc/frutc.rxmlhttp://ww2010.atmos.uiuc.edu/(Gl)/guides/maps/utc/frutc.rxmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/index.shtmlhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/observations.htm#tophttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklisthttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/equipment.htm#checklist


15/15

____ Monitor the receiver (logging), antenna setup (plumb), and battery health (good).

____ Terminate the session at the scheduled stop time; turn off the receiver.

____ Acclimate the meteorology equipment; measure and record weather observations.

____Reconfirm that the antenna is still plumb over the station and remeasure the antenna

height in meters and feet.

____Record the antenna height in the "After" column on the observation log; check the form

for completeness.

____ Tear down the equipment; depart the station site and return to the office.

____Download the data directly from the receiver into your computer hard-drive twice (to

ensure clean copies) then copy to diskette.

____Ensure sufficient memory is available in the GPS receiver for the next session; delete

older sessions if necessary.

____ Recharge batteries for the next session.

____

Check and verify all entries on the NGS Observation Log, Pencil Rubbing

Form, Visibility Obstruction Diagram, and Station Description.

____Ship data to the Project Coordinator.
http://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#downloadhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#visibilityhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#datasheethttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#shiphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#shiphttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#datasheethttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#visibilityhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#pencilrubhttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#obsloghttp://www.ngs.noaa.gov/PROJECTS/GPSmanual/data.htm#download

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