Connectivity Methodology Ver. 3.0

NRDC Sustainable Cities Team

Presenter: TL

July 15,2015

Many thx to RND team!

Outline

• Key updates

• Principles

• Input preparation

• Interim procedure

• Output result

• Evaluation of the Methodology

Key Updates

• Powerful ArcGIS (licensed authorization!)• Overcome some constrains posed by KMZ preparation

• Generate random points

• Select eligible points

• Batch: python code

• Update of Cityname.xlsx file• Skipping of sheet Random_Points

• Important annotation: the unit of average altitude is kilometers

Principles

• The process will…• generate 1000 random points for each city;

• Increasing capacity is feasible

• allow us to choose 40 eligible points to measure the walking distances;• Identify if the interim points meet the standard (od distance = 500m)• Discard the points that do not meet the requirement• Go back to the bank test if a new eligible point meet the requirement

• get average walking distances from the final 40 points;

• The process need to be…• strictly random in point selecting• accurate in calculating the distance • comparable across all cities• efficient

Input Preparation

• Google Earth Pro: • citynameRND.kmz (Many thanks to Ning, Xiao, Judy, Chenzi, Danlu)

• Same setting requirement: degree (decimal)

• Microsoft Excel:• cityname.xlsx

• (Random_Points_Value), Eligible_Points, (Eligible_Points_Raw), Square_Points, Distance

• ESRI ArcGIS 10.X:• Manually geoprocessing• Python stand-alone processing

• (Windows environment is strongly recommended!)

• VPN and good network

Interim procedure: RP gen and EP selection

• In ArcGIS:• KMZ to Layer• Feature class to feature class

• (transforming boundary polylines into polygons)

• Generate random points: CITYNAME_RP.dbf• (confined by boundary polygons)

• Selecting eligible points: CITYNAME_EP.dbf

• Detailed procedure: consulting to the python file

• In Excel:• Copy and paste fields: Name, Latitude, Longitude

• From CITYNAME_RP.dbf to sheet Random_Points_Value• From CITYNAME_EP.dbf to sheet Eligible_Points_Value (1 st round EP)

Interim Procedure: Square Points

• In workbook Square_Points of Nanchang.xlsx:• Fill value of Nanchang’s average altitude in the cell following Average

Altitude;

Interim Procedure: Distance

• In workbook Distance of Nanchang.xlsx:

• Copy the cells in column C (Output);

• In GE Pro;

• Select “Search Google”;

• Paste the value in box to the left of “Search” button;• Make sure no space after the last character!

• Otherwise GE will recognize this syntax as an error.

• Click on “Search” button;

Interim Procedure: Distance (Con’t)

• In GE Pro;

• Read the distance;

• In workbook Distance ofNanchang.xlsx:

• Record the original value (unit: meters) in corresponding cell in column E;• Do not worry about the weird

direction/distance you get now.

Interim Procedure: Distance (Con’t)

• Check for reasonableness• If the trip origination and trip

destination are approximately located at the point eligible points…

• You are lucky!

Interim Procedure: Distance (Con’t)

• Check for reasonableness• If the trip origination and trip

destination are not at the intended places…• (distance between origination and

destination <> 500m)

• Too long

• Too short

• Mark the corresponding cell in column I as problematic • E.g. “*od<>500”

• (need to specify the error type?)

Interim Procedure: Distance (Con’t)

• Complete all 160 (4 square points of each eligible point * 40 eligible points) entries• Good luck!

• Review the notes for problematic results;• You have made marks for each pair of eligible point and square point;

• Look at column I;

• Check if the note belongs to a problematic eligible point• If more than 3/4 (including 3/4) direction/distance results of the eligible point

are marked as problematic, we need 2nd round of eligible points selecting;

• Clear all four results of the problematic eligible point in column E

Interim Procedure: 2nd round Eligible Points

• In workbook Eligible_Points of Nanchang.xlsx:

• Mark all problematic eligible points

• Find the first backup eligible points…• Directly from Nanchang_RP layer in GE

• Manually replace the number of the problematic eligible point in column A with the one of backup eligible point;

• Use a point from the back up list generated in 1st round• Use a point from the back up list generated by ArcGIS

• (time saving)

• Repeat the Interim procedure: Distance• If the back up point is still problematic, continue the process of finding new back up

eligible point.

• Finish the process when no problematic eligible points show up.

Output Result

• Save Nanchang.xlsx. • The results will keep in workbook Distance;

Output Result

• Copy column B, C, and D to Nanchang_EP.csv; • Save Nanchang_EP.csv;• No need to copy column A;

• Copy column C, D, and E to Nanchang_Square.csv; • Save Nanchang_Square.csv;• No need to copy the rest columns;

• Import Nanchang_EP.csv and Nanchang_Square.csv to Nanchang.kmz in GE Pro; • Same procedure of importing Nanchang_RP.csv;• Use different colors;• Be sure to save to My Places;

• Save as Nanchang_Square.kmz;

Evaluation

• The estimated time of finishing one city is 2-3 hours.

• The majority of the process could be documented.

• Use ArcGIS can help increase the randomness in selecting eligible points• Strongly depend on the accuracy of boundary and RND boundary

• Batch processing allows for massive amount of cities to be measured

• Strictly randomness in RP and EP selecting process

• Overcome the inconsistency of different coordinate systems• WGS-84 and GCJ-02 coordinate system

• Points are random, so the relative location between points and road network is of no necessary importance in the process.

Evaluation

• In Interim Procedure: Distance, it would allow at ½ of the results to be inaccurate, which generate inaccuracy.• Tolerance level could be lower by only allowing no more than ½ result to be

problematic• < 500m is calculated as 500m

• Hard to decide whether the distance between an od pair is 500m• Usually not!

• How close?

• Both not accurate, but the distance seems to be 500m?

THX!