Extract Lat/lon from Shapefiles

I have a grid projected in a Cartesian coordinate where each point represents a portion of a terrain. And I'd like to know the distance between each of these points to the closest road.

These roads are in a shapefile, and the function I'm using ipdm needs a XY input (as my grid point in Cartesian coordinates). So, my thinking is somehow extract the lat/lon of the roads, convert to a projected coordinate, ad then use the ipdm .

Any thoughts?

Answer 1

[Chad Greene]

You should be able to use shaperead with the 'UseGeoCoords',false option to get roads in cartesian coordinates. Just make sure the projection associated with the shapefile is the same projection you're using for your data.

[Igor Noberto]

I tried with the shaperead, but seems that the data I'm taking is incomplete. See,

Using the option 'false':

roads = shaperead('Rodovias.shp','UseGeoCoords',false);
Y = (roads.Y);
X = (roads.X);
scatter(X,Y);

The result is:

What is plenty different from:

roads = shaperead('Rodovias.shp','UseGeoCoords',true);
Y = (roads.Lat);
X = (roads.Lon);

Seem like I need to access other type of data.

[Chad Greene]

I assume the road coordinates are in a structure array, so I wouldn't expect scatter(roads.X,roads.Y) to plot all the roads. What happens if you do

[X,Y] = polyjoin(roads.X,roads.Y); 
plot(X,Y)

[Igor Noberto]

using this, I received:

Error using polyjoin
Expected input number 1, LATCELLS, to be one of these types:

cell

Instead its type was double.

Error in polyjoin (line 20)
    validateattributes(latcells,{'cell'},{'vector'},mfilename,'LATCELLS',1)

Error in script11 (line 22)
[x,y] = polyjoin(X,Y);

Then, I made the double to cell conversion using num2cell, but I got the same result from the post above.

I'm not sure what I'm doing wrong.

these are the roads contents:

>> roads

roads = 

6492x1 struct array with fields:

      Geometry
      BoundingBox
      X
      Y
      id
      br
      uf
      codigo
      local_de_i
      local_de_f
      km_inicial
      km_final
      extensao
      superficie
      federal_co
      federal__1
      federal__2
      estadual_c
      superfic_1
      mpv_082_20
      concessao_