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Skyline Graph with multiple observer points

KellyMaloney

Hi all,

I have ~2000 observer points and associated skylines created from the Skyline tool. I wish to use the skyline graph tool to estimate the visibility ratio for each of these points. However when I run the tool it only provides output for the first observer point. Is this a limitation to the skyline graph tool? I also would like to eventually export a table with visibility ratios for all 2000 points. Any thoughts/advice?

Thanks,
Kelly

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JanetWong

Hi Kelly,

I'm encountering the same problem. May I ask what is 'lines' in line 11 refers to? Is it referring to the lines generated by the tool 'Skyline'? But I have more than 9,000 points, it is difficult to generate the skyline...

NeilAyres

You may want to consider updating this to use the data access module :
http://resources.arcgis.com/en/help/main/10.2/#/SearchCursor/018w00000011000000/
Then you can get the length from the SHAPE@LENGTH token rather than trying to read the length attribute in the feature class.
Cheers,
Neil

JonathanGillespie

Hi Adam,
Were you able to get the python code to successfully work with your data set? I have tried applying it to my own data and am getting error messages after the table has been created and the first lot of temporary shape files have been created.

Cheers,
Ros

Hi Ros

I may or may not be correct here (very new to python) but I was trying to use the same script and found the same issue. I believe it can be resolved by changing the line

skyCursor = arcpy.SearchCursor(tmpSingleLineShp, "", "", "Length", "")

to

skyCursor = arcpy.SearchCursor(tmpSingleLineShp, "", "", "Shape_Leng", "")

It seems to work with the data points that I'm using (only two of them for the time-being).

If anyone can shed any light whether this is indeed the correct solution I would be grateful. As I said above - very new to Python!

Jonathan

rosalindkennerley

Hi Adam,
Were you able to get the python code to successfully work with your data set? I have tried applying it to my own data and am getting error messages after the table has been created and the first lot of temporary shape files have been created.

Cheers,
Ros

AdamHanna

You just saved me a whole lot of work, thanks!

KellyMaloney

Hi Adam,

Sorry about that. I most often use R, so I forget about the indentation issue with python. See the attached python script.

Kelly

Topographic_shade_example.py.zip

AdamHanna

Hey Kelly,

This is great, thanks! However, it appears that when you copy/pasted, all of the indentations were removed from the original python code? Python is very dependent on proper indentations. Would you mind uploading the .py? Or, maybe there's another way to paste the code and keep the indents in tact?

KellyMaloney

Hi Adam,

I hope your work-around did what you needed. I actually worked with a python coder who created the following script. This worked perfect and gave me my needed values in a stand-alone csv file. Hope it works for you.

-Kelly

import os

import arcpy
from arcpy import env
arcpy.env.overwriteOutput = True
# Obtain a license for the ArcGIS 3D Analyst extension
arcpy.CheckOutExtension('3D')

# Set local variables
outLocation = r"C:\Users\Desktop\Topographic_shade\Topographic_shade"
inputDataLocation = r"C:\Users\Desktop\Topographic_shade\Topographic_shade"

points = "DR_CenterLine_Dissolve_pointsZ2Da_elev3Dt.shp"
lines = "DR_CenterLine_Dissolve_pointsZ2Da_elev3D_skyline_originalDEMb.shp"

pointsFile = os.path.join(inputDataLocation, points)
linesFile = os.path.join(inputDataLocation, lines)

# Set environment settings
env.workspace = outLocation

# Process: Create the empty table
outputFName = os.path.join(outLocation, "Shade_original_DEM.csv")
outputFile = open(outputFName, "w")

outputFile.write("ID,PercentOpenSky,PercentShade,MeanHorizAng,MeanZenithAng\n")

fcCursor = arcpy.SearchCursor(pointsFile)
for row in fcCursor:
    print(row)
    #create a temp shapefile with just one of our points
    whereClause = '"FID" = ' + str(row.FID)
    tmpSinglePointShp = os.path.join(outLocation, str(row.FID) + ".shp")
    arcpy.Select_analysis(pointsFile, tmpSinglePointShp, whereClause)
    tmpSingleLineShp = os.path.join(outLocation, "sky" + str(row.FID) + ".shp")
    arcpy.Select_analysis(linesFile, tmpSingleLineShp, whereClause)
    skyCursor = arcpy.SearchCursor(tmpSingleLineShp, "", "", "Length", "")

    for rows in skyCursor:
        value = rows.getValue("Length")
        if value == 0:
            answerPercent = "NA"
            Shade = "NA"
            aveHoriz = "NA"
            aveZenith = "NA"
            outputFile.write(str(row.FID) + "," + str(answerPercent) + "," + str(Shade) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")

            arcpy.Delete_management(tmpSinglePointShp)
            arcpy.Delete_management(tmpSingleLineShp)
            print(str(row.FID) + "," + str(answerPercent) + "," + str(Shade) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")
        else:

            #run the skylineGraph on temp output file
            tmpSinglePointOutTbl = os.path.join(outLocation, "t" + str(row.FID) + ".dbf")
            arcpy.SkylineGraph_3d(tmpSinglePointShp, tmpSingleLineShp, 0, "ADDITIONAL_FIELDS", tmpSinglePointOutTbl)

            #manually calculate the average of the two fields we are interested in
            count = 0
            horizAngSum = 0
            zenithAngSum = 0
            for outputRow in arcpy.SearchCursor(tmpSinglePointOutTbl):
                horizAngSum += outputRow.HORIZ_ANG
                zenithAngSum += outputRow.ZENITH_ANG
                count += 1

            aveHoriz = horizAngSum / count
            aveZenith = zenithAngSum / count

            #this next section parses out their printed output and stores the 'Percent of sky in our CSV'
            msgText = arcpy.GetMessages()
            for line in msgText.split("\n"):
                if line.startswith("Percent of sky visible above a base vertical angle"):
                    answerPercent = line.split()[-1][:-1]
                    Shade = 100 - float(answerPercent)

            #write out the calculated answers to our CSV
            #outputFile.write(str(row.FID) + "," + str(answerPercent) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")
            outputFile.write(str(row.FID) + "," + str(answerPercent) + "," + str(Shade) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")

            arcpy.Delete_management(tmpSinglePointShp)
            arcpy.Delete_management(tmpSingleLineShp)
            arcpy.Delete_management(tmpSinglePointOutTbl)
            #print(str(row.FID) + "," + str(answerPercent) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")
            print(str(row.FID) + "," + str(answerPercent) + "," + str(Shade) + "," + str(aveHoriz) + "," + str(aveZenith) + "\n")

outputFile.close()

AdamHanna

I believe I may have found a workaround, but it's time consuming:

Convert the sklyine polylines to points (convert vertices to points)
Add X, Y and Z data to said points
Calculate Azimuths and Zeniths from the XYZ data and the OID XYZ data

Would really love for the Skyline Graph to be able to handle multiple observer points.....

AdamHanna

Hi Kelly,

I'm having the same problem. Did you ever find a fix?

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