Scrapes an Esri REST endpoint and writes a GeoJSON file.
If you just want to use the command line tool esri2geojson
, the recommended way to install this package is to create a virtual environment and install it there. This method does not require that you git clone
this repository and can get you up and running quickly:
virtualenv esridump
source esridump/bin/activate
pip install esridump
This module will install a command line utility called esri2geojson
that accepts an Esri REST layer endpoint URL and a filename to write the output GeoJSON to:
esri2geojson https://maps.six.nsw.gov.au/arcgis/rest/services/sixmaps/MaritimePublic/MapServer/13 martime_maps.geojson
You can write to stdout
by using the special output filename of -
(a single dash character).
You can also pass in the --jsonlines
option to write newline-separated (\n
) lines of GeoJSON features, which you can then pipe into other applications.
You can use this module in your code to get GeoJSON Feature-shaped Python dicts
into your code:
import json
from esridump.dumper import EsriDumper
d = EsriDumper('http://example.com/arcgis/rest/services/Layer/MapServer/1')
# Iterate over each feature
for feature in d:
print(json.dumps(feature))
d = EsriDumper('http://example.com/arcgis/rest/services/Layer/MapServer/2')
# Or get all features in one list
all_features = list(d)
The module will do its best to find the most efficient method of retrieving data from the Esri server, given the capabilities of the server. There are several strategies we use to get the data, described here in most to least efficient order:
In ArcGIS REST API version 10.3, Esri added support for pagination directly with the resultOffset
and resultRecordCount
parameters. Unfortunately, most servers don't support this feature because the backend SQL engine must also be configured to support it. So far, it seems that only the Esri-hosted layers support this feature reliably.
In ArcGIS REST API version 10.0, Esri added support for the server to return an exhaustive list of object IDs for all features in a layer. Once this list of object IDs is retrieved, we break it into chunks of maxRecordCount
queries using the objectIds
parameter.
In ArcGIS REST API version 10.1, Esri added support for performing various statistical queries on the server without requiring the client to download the whole dataset. On servers that support this and don't respond to the objectIds
queries, we will use a minimum and maximum statistics query to find the minimum and maximum values for the objectId
column, then build chunks of where
-clauses that narrow the range down to objectId
s between two fenceposts.
When a server does not support any of these methods, we'll make recursive quad-tree queries using bounding envelopes. We start with a query for the layer's entire extent
. If the server returns exactly the maxRecordCount
number of features, we split that extent
into 4 equal rectangles and query those. If those smaller queries return maxRecordCount
features, we split the rectangle again and continue until the server returns something less than the maxRecordCount
.
To suggest changes or improvements to this code, create a fork on Github and clone your repository locally:
git clone git@github.com:openaddresses/pyesridump.git # replace with your fork
cd pyesridump
We use Pipenv to manage dependencies for development. Make sure you have Pipenv installed and then install the dependencies for development:
pipenv install --dev
pipenv shell
Your changes to the code will be reflected when you run the esri2geojson
command from within the virtual environment. You can also run (and add) tests to check that your changes didn't break anything:
nosetests
This Python module was extracted from OpenAddresses machine
, which was inspired by code from koop
. A similar node/JavaScript module is available in esri-dump
.