GIS Utility Data: The Good The Bad and The UGLY · GIS Utility Data: The Good The Bad & The UGLY...
Transcript of GIS Utility Data: The Good The Bad and The UGLY · GIS Utility Data: The Good The Bad & The UGLY...
GIS Utility Data: The Good The Bad & The UGLY
Alan Jacobson, PE
704-651-5538
GIS a Tool for Managing & Analyzing Public Utilities
Most common use of GIS for utilities?Producing and Maintaining a set of System Maps (A task which is
perhaps only marginally easier in GIS than in earlier CAD based solutions).
Using GIS to manage or analyze a utility requires much more thought about the GIS design and potentially much more data acquisition than simple map makingResearch is required to determine how the data will interact with desired third party software packages for asset management, hydraulic modeling, and work order management.Planning for other common or occasional analyses and including any required data is best performed when implementing the GIS design well prior to starting the data gathering and data input processes.
Building or maintaining GIS data to meet complex needs may require:
Knowledge of the utility’s actual behavior
Knowing what information is available or could be made available for each asset
Understanding Data processes used in one or more third party software packages
Understanding of the advanced uses that may be needed at later dates
Know Your Data History
Many GIS Datasets were originally built or converted from data that was specifically used to create a map at only one scale.Each feature included may have been intentionally spatially altered and or scaled hundreds of times its true size so that it was clearly visible at that scale.Data from these sources frequently create GIS conflicts with other features and or normal construction standards.More recently GPS technologies have created an easy method of field capture of GIS features. But even with GPS some features may be closer together vertically or horizontally than can be determined by the GPS equipment being used.
Accuracy
After a GIS is built to “make maps” or is built without consideration of required accuracies don’t be surprised to find out that many uses require a specialized GIS conversion or repair process or in the very worst cases a complete rebuild of the entire dataset
GIS does not stand for “Get It Surveyed” nor does Accurate imply that a Survey is needed
Knowing precisely where key features are located can be very helpful
GIS Utility Locations: PrecisionAerial OrthophotosSub Meter GPSRTK GPSSurvey Levels
36” RCP@ 0.045 %
100 Ft
0.045 Ft
Rules & Exceptions
Edge-Junction cardinality ruleMultiple Features at same XY location
Lines & Point Features in Simple Edge GIS Networks
1
2
4 5
Nodes (Pipe Ends) = Pipes Connected +1 – Loops Completed
For Large Water System Networks: Nodes/Pipes < 1
7
3
4 5
6
1 6 2
3
AssumptionsTo Be or Not to Bea Point FeatureCorrect Answer Depends on the use:Distribution MainTreatment PlantPump StationModelingDesignWork Order
CAD Drawings & System Maps
CAD Drawings and System Maps
CAD Drawings and System Maps After Conversion
From CAD Drawings and System Mapsto Comprehensive Water, Sanitary, & Storm Sewer GIS complete with Asset Management & System Hydraulic Modeling
1440 Miles of Water Main = 130,000 Water Features
1470 Miles of Sanitary Sewer = 70,000 Sewer Features
844 Miles Stormwater =102,000 Storm Features
90,000 Water Customer Locations
CAD Drawings and System Maps Can Produce Ugly but Accurate GIS Data
50 Feet
CAD Symbols were drawn for a known plotting scale on paper. Placement required exaggerating the actual planned or as-built location of the features to make the symbols more legible
Improperly handled CAD Symbols can be the dominant linear GIS feature and if they contain hatch patterns can result in an explosion of lines
Frequently CAD line work was removed to make the symbol more legible
CAD Drawings and System Maps - Symbols
20 Ft
15.5 Ft
2.7 Ft
Removed
or Trimmed
Why do I have hundreds of thousands of short pipes?Our city has 250 miles of Water Main, Why do I have 650 miles of pipe in GIS?
Bad Information from Any Source Makes BAD GIS
28% Slopes
Perhaps the Surveyed Stormwater Grate Inlet is not 74 feet Deep
Negative Slopes
4111691169000Hydrant_2004_NAD83_New
6298210981981Hydrant
16234036100523923397Water Valve
021051621Water Manhole
10273048225273Meter
213121012Water Vault
011000Water Treatment Plant
072055Water Tank
010011Pump
03582-1357356Cap
040044Increaser
052025052Reducer
823633187827543632Fitting
Duplicate Features
Total Features
Incorrect Position
Required Pipe Splits
Snapped to Endpoint
Snapped to LineGIS Feature Class
CAD Drawings and System Maps
What visually looks like 1 feature is often a collection of features or a series of duplicate and near duplicate GIS features
TEE1600571263.8373029231237055.06892079
CROSS1601571254.5370789141237039.40684078
CROSS1518571254.5370789141237039.40684078
TEE1602571232.6050468931237038.98853678
TEE1519571232.6050468931237038.98853678
TEE1603571239.37419891236934.48370468
TEE1520571239.37419891236934.48370468
TEE1604571262.1310629211236928.55397668
TEE1521571262.1310629211236928.55397668
TEE1513571315.8027429711236255.69074405
TEE1597571315.8027429711236255.69074405
TEE1514571306.0696229621236255.27474405
TEE1598571306.0696229621236255.27474405
901599571279.0687909371236253.94252005
901515571279.0687909371236253.94252005
TEE1512571336.843126991235959.17925577
TEE1596571336.843126991235959.17925577
TEE1700570064.0892058051235691.00927152
TEE810570064.0892058051235691.00927152
TEE1511571415.6458150641235273.12869513
TEE1595571415.6458150641235273.12869513
TEE1594571945.2376235571234019.56248597
TEE1510571945.2376235571234019.56248597
TypeOBJECTIDYX
Fitting Duplicates
Line1732576878 7157721521245222 2300164Line803572862.5521844111245042.71436823Line2723572862.5521844111245042.71436823Hydrant2721572905.5105204511245038.80908823Hydrant801572905.5105204511245038.80908823Line802572873.4869684221245036.46592023Line2722572873.4869684221245036.46592023Hydrant1743576891.4074841641244888.17920009Hydrant2766576891.4074841641244888.17920009Line1763576898.9735641711244877.37036808Line2767576898.9735641711244877.37036808Line1735576908.650108181244797.925632Line2765576908.650108181244797.925632Hydrant1713574057.4134975241244567.26783979Hydrant2754574057.4134975241244567.26783979Line2755574063.245689531244553.27052778Line1714574063.245689531244553.27052778Line1712574065.9674815321244372.08294361Line2753574065.9674815321244372.08294361Line1034569643.8462614141244188.21657544Line73569643.8462614141244188.21657544Hydrant1033569649.2801174191244140.51891139Hydrant72569649.2801174191244140.51891139Line1036569713.4849174791243184.2063345Line75569713.4849174791243184.2063345Hydrant1035569707.5930774731243183.2243185Hydrant74569707.5930774731243183.2243185Hydrant42570214.9000859461242368.56524574Hydrant1011570214.9000859461242368.56524574Hydrant1031574775.4466501931241878.52774129Hydrant67574775.4466501931241878.52774129Line1030574760.2725061791241838.52338925Line52574760.2725061791241838.52338925Line1890564049.6950882041241202.04082866Line13564049.6950882041241202.04082866Line1032569229.9569810281241055.18489252Line68569229.9569810281241055.18489252Line1916566668.0556666421233927.10066188Line1566668.0556666421233927.10066188Line5567292.3664512241233794.62782976Line1917567292.3664512241233794.62782976
TypeOBJECTIDYXWater Valve Duplicates
Duplicate Features:
Pipes Not Split or
Connected
Pipes Not Split or
Connected
Does GIS agree with Construction drawings?
Intersecting & Non-Intersecting Pipes.
Pipes Not Split or
Connected
Does GIS agree with Construction drawings?
Intersecting & Non-Intersecting Pipes.
Pipes Not Split or Connected
No construction drawings
OK Pipes Not Split or
ConnectedPipe Split
@ Tee
Pipes Split @ Tee
After GIS compared to original construction drawings?
Intersecting & Non-Intersecting Pipes.
Pipe Split @Valve
Pipes Split @Tee
Pipe Split
@Valve
Hydrants GPSed by city fire fighters
Many original GIS positions were much better than the Newly GPSed locations
Not all of the GPS work included getting out of the fire truck
45 Ft
Move the New Hydrant to the old position or to the position visible on Orthos, Check Old Hydrant for missing Data, reconnect and reposition Pipes, Valves, and Fittings as required
Pipes not Split, Symbols not Rotated
Pipes not Split
Pipes not Split
Pipes not Split
Symbols not Rotated
Pipes not Split
Pipes Split Symbols Rotated
Pipes Split
Pipes Split
Pipes Split
Symbols Rotated
Symbols Rotated
For a wide number of tasks (including system maintenance, map production, and modeling) it is important to be able to quickly distinguish all mains verses all service laterals.
Shown in dark Purple is a single CAD Sewerline. It is labeled as 24” and further West as 8”.
All line work in GIS was trimmed at the map “grid” edgesEdge matching and Reconstruction required for all features that cross map boundaries: Common in CAD and GIS Data (ArcInfo LIBRARIAN tiles)
CAD Drawings and System Maps – Valves Not Connected to Pipes
CAD Drawings and System Maps – Everything as one Shape FileSeveral thousand CAD features exported as a single ESRI Shape file “The proposed
Sewer Interceptor”. Less than 1% of the features were related to the interceptor.
Arcs and Symbols From CAD to Shape File to GeoDatabaseShape files cannot store curves. When true curves from
CAD or ArcGIS are converted to shape files, a single line with an arc segment becomes a line with multiple straight segments and vertices along the line at roughly 1 vertex point per 2 degrees of arc. Any curved pipes or imported “point / line” symbols containing circles or arcs are subsequently made into fairly complex and difficult to edit GIS features. This is BAD!!
If receiving data from unknown sources look for signs of Bad processes
Somewhere along the conversion path processes that split multiple part line segment features into individual short line features.
Pipes, Arcs, and Symbols
How many waterlines are shown along Saddlebrook Dr?54
Water System Arcs and Symbols
How many waterlines are shown along GlenEagles Lane?118750181
CAD Drawing TechniquesCAD system-Valves, Fittings, and Hydrants were drawn once and then stored as a Symbol or “Block”
Unfortunately routines are often used in CAD which convert blocks back into the original symbol’s arcs, circles, and lines. For this Utility all Hydrants and Valves in CAD were present on the water main layer as lines and Arcs
Can Good CAD Information be Converted to BAD GIS?
Shown as Red Dots are pipe endpoints that should be snapped to Sewer ManholesRed Crosses represent other problem locations.
Missing Features?Take advantage of ESRI’s Edge-Junction Cardinality rule capabilities or other Rules and Tests that are available using ArcObjects
Missing Hydrant Laterals
Missing Water lines
Attributes in GIS based on the nearest CAD text string
Spatially tied pipe to even when that distance is thousands of feet away
Pipes labeled as ARVs
Pipes need attributes not a string of text that must be read and interpreted prior to use
Sewer and Water Shapes compared to Surveyed Water and Sewer Locations
Hydrants are in Wrong Locations 58 Feet from older Surveyed Data
Water lines shown over 30 feet from surveyed valve locations
Water lines Not shown in New GIS shape files
Is it Good if Its Missing?
With Diameter Percent
With Material Percent
With Date Percent
Date Range
257 2.0% 132 1.0% 964 7.5% 1979-2002
SourceDate
Modified Pipes Feet MilesCatawba County Waterlines 2/3/2003 12,789 4,228,916 800.93
Position Artifacts
Model Quality GIS Utility Data
Despite misconceptions, GIS Data can be Model Quality even when Key Features have Significant Positional errors (30 ft or more) and when lengths of connecting pipes or cables are unrealistic
IF:Correct number of features and attributes are presentConnectivity between features has been correctly established
Model Quality does not mean perfect. Model quality simply means that the results of using the data for modeling produces answers that are useful and accurate within desired limits.
The UGLY Truth of BAD Data
1.6 Ft Gap
Test the DataTesting Utility GIS layers for errors and or compatibility with
desired processes or software packages can determine if the system is:GoodBad - Unsuitable for desired uses
UGLY - but otherwise Ok for several usesAs long as you Don’t send Robbyto find the Hydrant @1,254,783.034
497,904.935
Fire Hydrant Not Found @
Coordinates, Do You want me to
Dig Deeper?