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How do I search a shapefile using GPS coordinates?

I have a standard shapefile. It contains many shapes with their attributes.
I have a list of GPS coordinates that I know for sure are within the area of that shapefile.
How -- preferably with Python -- can I supply the lat/long and get an handle to that shape?

Molnár István

Hi,

you could try this python libraries:
1. pyshp
2. pyshapelib
3. shapelib

Hope it helps,
Istvan

Francois Koutchouk

ASKER

Thank you, I've tried 1 but cannot see how I could find the index of a shape (record) by supplying a GPS point (lat/long).

Molnár István

i never used this library, but i made a simple app in python, hope it gives you some idea:

code:

import shapefile
sf = shapefile.Reader("shapefiles/blockgroups.shp")
sf = shapefile.Reader("shapefiles/blockgroups.dbf")

#with shapefile.Reader("shapefiles/blockgroups.shp") as shp:
 # print(shp)

shapes = sf.shapes()
pointindex=-1
shapeIndex=-1
for shape in shapes:
  shapeIndex=shapeIndex+1
  for point in shape.points:
    pointindex=pointindex+1
    #print('shape[idx:',shapeIndex,']= X(',point[0],'),Y(',point[1],')','\n')
    if (point[0]==-122.465628 and point[1]==37.66665) or (point[0]==-122.469816 and point[1]==37.675509):
      print('Found Coordinate ! Shape index: ', shapeIndex,', Point index: ',pointindex)

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you can try it in the online compiler:
Link to Code

hope it helps
Istvan

Molnár István

the shape file in google maps looks like this:

Link to Google Maps

Francois Koutchouk

ASKER

Excellent! The code gives me all the points of the shape. Providing the lat/long of any of those points identifies the shape.
The question is how do I know if the lat/long is within the polygon defined by the lines connecting those points?

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Molnár István

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Francois Koutchouk

ASKER

Fantastic answer, thank you very much.