Shapefile Conversion – How to Convert SHP to GPX or JSON

convertgeojsongpxogr2ogrshapefile

I would like to convert the tree inventory shape files of London (Canada) into a GPX file and if possible into a JSON file. You can download the archive from their Open Data website. It contains the following files.

READ_ME.txt
TREEINV_SPECIES.xml
TREEINV_SPECIES.xsd
TREES.DBF
trees.gpx
trees.sbn
trees.sbx
trees.shp
trees.shp.xml
trees.shx

Today, I stumbled into ogr2ogr and tried the following command.

$ ogr2ogr -f GPX trees.gpx trees.shp

Though, the following error occurs.

ogr2ogr ERROR 1: Latitude is invalid. Valid range is [-90,90].  
This warning will not be issued any more

I already found a similar question but cannot figure out what the problem is. Please mind, I am totally new to the topic of converting geographic data. If you know any better tool I am willing to try it out.

EDIT: An initial success story.

According to the answers of Aragon and Brent Edwards I came up with the following commands. I found a webpage stating that data can be ordered in NAD83. So I assume that the dataset I am trying to convert comes as NAD83 as well. However, I cannot understand how I can find out the EPSG resp. SRID myself. With the given information I can lookup EPSG:26917 in the EPSG Geodetic Parameter Registry – but if I have no clue what the number is – how would I do that?

$ ogr2ogr -f GeoJSON -s_srs EPSG:26917 -t_srs EPSG:4326 trees_coordinates.json trees.shp
$ ogr2ogr -f GeoJSON -s_srs EPSG:26917 TREES_properties.json TREES.DBF

The converted GeoJSON files contain the following data.

// Example rows from trees_coordinates.json
{
"type": "FeatureCollection",
"features": [
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.233494, 42.994146 ] } }
,
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.232346, 42.994477 ] } }
,
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.232176, 42.994527 ] } }
,
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.245137, 42.971636 ] } }
,
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.189495, 42.996498 ] } }
,
{ "type": "Feature", "properties": { }, "geometry": { "type": "Point", "coordinates": [ -81.189651, 42.996442 ] } }

]
}

And ..

// Example rows from TREES_properties.json
{
"type": "FeatureCollection",
"features": [
{ "type": "Feature", "properties": { "TREEID": 19.000000, "DIAMETER": 53.000000, "SPECIES": "MASU" }, "geometry": null }
,
{ "type": "Feature", "properties": { "TREEID": 23.000000, "DIAMETER": 30.000000, "SPECIES": "MANO" }, "geometry": null }
,
{ "type": "Feature", "properties": { "TREEID": 24.000000, "DIAMETER": 53.000000, "SPECIES": "MASI" }, "geometry": null }
,
{ "type": "Feature", "properties": { "TREEID": 104920.000000, "DIAMETER": 5.000000, "SPECIES": "OAWH" }, "geometry": null }
,
{ "type": "Feature", "properties": { "TREEID": 60358.000000, "DIAMETER": 34.000000, "SPECIES": "MAMA" }, "geometry": null }
,
{ "type": "Feature", "properties": { "TREEID": 60355.000000, "DIAMETER": 51.000000, "SPECIES": "MASU" }, "geometry": null }

]
}

Questions:

  1. Are my commands correct?
  2. How can I match the rows of both files? Which property set belongs to which GPS position? Is their a way to combine both in one file? I saw another format that includes all information in one file.
  3. How can I find out the EPSG/SRID and SRS in general if I have nothing more than those files listed in the beginning of my question?

Best Answer

To answer my own question on how to combine both the .dbx (properties) and the .shp (geometries) into a single JSON file: The problem I did not see is that all file names must be lower case to enable ogr2ogr to do the conversion. That should not be neccessary if your file system is case-insensitive but mine is. With this requirements fulfilled ogr2ogr is able to associate the .shp and .dbx files with each other. - The command is the following.

ogr2ogr -f GeoJSON -s_srs EPSG:26917 -t_srs EPSG:4326 trees.json trees.shp

Here is another link that might be of interest in this context. This webpage allows to read the projection information from a .prj file.

Related Question