[GIS] Creating random points only within multipart polygon and none outside using ArcMap

arcgis-10.3arcgis-desktoparcmaprandomshapefile

I am currently using a shapefile consisting of an area smaller than the entire study boundary ie. I want this to to be my overall study area. I used a raster to polygon tool and converted it to a shapefile and used the Dissolve tool to create a multipart polygon.

Now when I am creating random points and specify the constraining feature class, it is creating random points outside the polygons I possess as well. Attached is a screenshot of random points all over, instead of just within the polygons.

Best Answer

Another option is the Sampling Design Tool, which gives you the option of how to place random points...inside any feature or by specifying the number of random points in features with specific attributes.

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[GIS] How to create random points outside polygons

Personally I do not like the random point algorithm in ArcGIS. Alternatively, use Geospatial Modelling Environment's (GME) genrandompnts function. You will be able to identify specific polygons where random points will be excluded (see highlighted area in attached .jpg). Best of all this software is free.

GME provides you with a suite of analysis and modelling tools, ranging from small 'building blocks' that you can use to construct a sophisticated work-flow, to completely self-contained analysis programs. It also uses the extraordinarily powerful open source software R as the statistical engine to drive some of the analysis tools. One of the many strengths of R is that it is open source, completely transparent and well documented: important characteristics for any scientific analytical software.

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[GIS] Creating Random Points that respect minimal distance across features / strata using ArcGIS for Desktop

I had initially posted the question on geonet. The matter being rather urgent, I posted the question here as well when I didn't recieve an answer there. In the meantime, Xander Bakker posted an excellent script that solves the problem neatly. The full answer can be view here, this is the section that solves the problem (with some slight modifications from me).

import arcpy
import random
import math

def main(path,fc_pol,fc_pnt,fc_mp,min_dist,number_of_points):
    # path = path for the input and output data
    # fc_pol = name of the input polygon shapefile
    # fc_pnt = name of the output point shapefile
    # fc_mp = name of the output point shapefile, used for visualization it and some manual checking
    arcpy.env.overwriteOutput = True

    arcpy.CreateFeatureclass_management(path, fc_pnt, "POINT")
    arcpy.CreateFeatureclass_management(path, fc_mp, "POINT")
    lst_all_pnts = []
    lst_mp = []
    cnt_pol = 0
    with arcpy.da.SearchCursor(path+fc_pol, "SHAPE@") as curs:
        for row in curs:
            cnt_pol += 1
            # print "polygon: {0}".format(cnt_pol)
            polygon = row[0]
            lst_pnts = []
            sr = polygon.spatialReference
            # create points inside polygons
            while len(lst_pnts) < number_of_points:
                print " - len(lst_pnts)={0}".format(len(lst_pnts))
                lst_pnts, bln_ok = add_random_point(lst_pnts, lst_all_pnts, polygon, min_dist)
                if bln_ok == False:
                    # saturation reached
                    print "saturation reached"
                    break
            # write points
            if len(lst_pnts) > 0:
                mp = create_multipoint(lst_pnts, sr)
                lst_mp.append(mp)
                lst_all_pnts.extend(lst_pnts)

    # create outputs
    sr = polygon.spatialReference
    lst_pntgeom = create_pointgeometry_list(lst_all_pnts, sr)
    arcpy.CopyFeatures_management(lst_pntgeom, path + fc_pnt)
    arcpy.CopyFeatures_management(lst_mp, path + fc_mp)

Best Answer

Related Solutions

[GIS] How to create random points outside polygons

[GIS] Creating Random Points that respect minimal distance across features / strata using ArcGIS for Desktop

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