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ArcGIS JSON to GeoJSON does not always work

GregoryGiguashvili

I'm reading ArcGIS Server responses with conversion to GeoJSON format as described in http://gis.stackexchange.com/questions/13029/how-to-convert-arcgis-server-json-to-geojson post.

1. I've tried to search any explanation on how this conversion works, but I could not find anything. Could anyone provide pointers to how this query-based conversion works in general?

2. The above mentioned technique does not work for some Feature Server layers, returning empty results.
This one works fine:
http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/Hydrography/Watershed173811/FeatureServer/0/query?where=objectid+%3D+objectid&outfields=*&f=pjson

This one returns empty result:
http://sampleserver3.arcgisonline.com/ArcGIS/rest/services/BloomfieldHillsMichigan/LandusePlanning/FeatureServer/2/query?where=objectid+%3D+objectid&outfields=&f=pjson

Could anyone explain why and how the problem may be solved?

Thanks a lot
Giga

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JonHall

After a freaking hour plus, I have determined that ArcGIS Desktop 10.6.1 "Features To JSON" with the GEOJSON option ONLY WORKS with SHAPEFILE INPUT.

Come on, ESRI....

"Features To JSON" repeatedly crashed, after output for the first few polygons, on the 4th or 5th polygon geometry, WHEN USING a FILE GEODATABASE OR ARCSDE polygon FEATURECLASS INPUT.

I tested with 3 or 4 different polygon featureclasses that were in WGS84, whether or not within a featuredataset, in FGDB or SDE, no matter, it crashed every time with a useless "99999" err msg. The log file was also useless. Clearly it was choking when reading geometry.

Copy the same featureclasses into shapefiles, and the GEOJSON output option works fine.

ESRI, I can't believe your code doesn't support FGDB or SDE, only supports legacy shapefiles as input. And you want me to move to Pro...LMFAO

I'm sorry this is in the wrong forum...

sarahzohar

Now I'm trying to use ArcGIS to convert JSON to GeoJSON Terraformer

GregoryGiguashvili

I'd like to respond to my own question for the benefit of others that may have encountered a similar problem.

The following special cases (at least) need to be considered when reading ArcGIS data using 3rd party client libraries:

Clients may not be able to process GeoJSON results containing UNICODE characters (\uABCD style)
ArcGIS limits the amount of objects returned per single query (usually to 1000), so iterators should be used
Empty feature sets may not be accepted by clients

This means that special care needs to be taken by the application client code for GeoJSON output returned by ArcGIS before passing it over to 3rd party libraries.

GregoryGiguashvili

It's still not fully clear how to query ArcGIS server so that it returns "features" in the ESRI Json output. This goes back to my original question. What query is supported for getting the "features" geometry from ArcGIS Feature Server?

I think I understand the problem now. It seems to be in servers configured with MaxRecordCount=1000 attribute, so queries returning more than maximum records simply fail. I wonder if there's a recommended technique for pulling all geometry data from the server?

For example, using "returnIdsOnly=true" would return all the feature ids, which the client could iterate later. Can someone provide more information/example on the most effective technique for iterating features using REST API?

GregoryGiguashvili

Ok, if you need make it client side you can run your query (arcgis js) and then you can use https://github.com/Esri/geojson-utils/blob/master/src/jsonConverters.js and convert featureset in geojson

Thank you for the link. By examining the Leaflet example of GeoJson-Utils, it looks like this is exactly what I need.

However, I'm still confused about this issue and I would appreciate more information on the topics below:

1. The main page of GeoJson-Utils package contains the following text:

Anybody looking to convert between Esri JSON and GeoJSON should check out the repository https://github.com/Esri/Terraformer. Terraformer contains a GeoJSON converter and a lot more functionality.

Could you please explain what is meant by this statement? These utilities really complement each other as I see it, but maybe I'm missing something.

2. It's still not fully clear how to query ArcGIS server so that it returns "features" in the ESRI Json output. This goes back to my original question. What query is supported for getting the "features" geometry from ArcGIS Feature Server?

Thank you
Giga

MarcoBoeringa

Unfortunately, Server Object Extension (SOE) is not helpful because we do not control what extensions are installed on the customer servers. We're interested to get the converted data from server using techniques officially supported by Esri, or convert the data on the client side.

Looking at that blog that Domenico pointed out, and the tools ESRI seem to offer to deploy such a SOE on the server as presented therein, I wouldn't consider SOEs "unsupported techniques" in the context of ArcGIS for Server...

nicogis

Ok, if you need make it client side you can run your query (arcgis js) and then you can use https://github.com/Esri/geojson-utils/blob/master/src/jsonConverters.js and convert featureset in geojson

GregoryGiguashvili

Have you tried using Esri's Terraformer libraries to do the conversion?

I'm now trying to use Terraformer for converting ArcGIS JSON to GeoJSON, so that it's later processed by GDAL/OGR library. Are there any pointers on how to supply a proper query to ArcGIS server so that the output can be fed into Terraformer.ArcGIS.parse function?

GregoryGiguashvili

you can create a soe. Here you can see an example: http://blog.geomusings.com/2013/06/10/geojson-from-arcgis-server/

Unfortunately, Server Object Extension (SOE) is not helpful because we do not control what extensions are installed on the customer servers. We're interested to get the converted data from server using techniques officially supported by Esri, or convert the data on the client side.

nicogis

you can create a soe. Here you can see an example: http://blog.geomusings.com/2013/06/10/geojson-from-arcgis-server/

GregoryGiguashvili

My problem is that I need GeoJSON output from ArcGIS server because that's what my GDAL-based client application expects to process. The queries that I posted in my initial question use a technique for converting Esri JSON to GeoJSON by providing "query?where=objectid+%3D+objectid&outfields=*&f=pjson" suffix to the service URL. This technique is described in http://gis.stackexchange.com/questions/13029/how-to-convert-arcgis-server-json-to-geojson post, but it's not explained.

My questions boil down to:
1. How the mentioned conversion technique works in general?
2. Why the technique does not work for some layers?

Thanks a lot
Giga

AnttiKajanus1

I tested the services by using query tool that is provided by REST endpoint by :

1) QUERY it seems to return results.

2) QUERY seems to return no results so I guess the service is empty so it returns correct information.

Can you specify your current problem in more detail since I didn't get that.

GregoryGiguashvili

The problem is that Esri/Terraformer parser is written in JS and my project is cross-platform C++ on the client side. I've seen this tool and I may be forced to use it in some awkward way if there're no other choices. Also, the main reason for not using Esri C++ libraries is the lack of 64 bit cross-platform support.

Any pointers on how and why the URL query works at all? Is it some kind of an undocumented behavior with Ersi ArcGIS?

JeffJacobson

Have you tried using Esri's Terraformer libraries to do the conversion?

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