How to force ogr to treat JSON mapserver query as "Multiline" instead of "Line" geometry type?

Question

I have a script that obtains feature data from a JSON output of an ArcGIS REST MapServer. At present my script treats the JSON data as a "LineString" Geometry type, but, the JSON data is in fact a "MultiLineString" Geometry type. How do I force my script to treat the data as "MultiLineString"? My current script is:

import ogr

url = 'http://maps.six.nsw.gov.au/arcgis/rest/services/sixmaps/LPIMap/MapServer/16/query?geometry=16501408.594,-4372525.989,16523000,-4320000&geometryType=esriGeometryEnvelope&f=pjson&outFields=functionhierarchy,OBJECTID,shape,roadontype,roadnamestring,shape_Length'

ds = ogr.Open(url)
lyr = ds.GetLayer()

if (lyr.GetGeomType() == ogr.wkbLineString):
    print ('line')
elif (lyr.GetGeomType() == ogr.wkbMultiLineString):
    print ('multiline')
else:
    print ('neithor line nor multiline')

del ds, lyr   

The JSON data is a MultiLineString type as it consists of seperate lists of many cordinates within a large single list. For example, the JSON output below shows the end of one list of coordinates and the beginning of a subsequent list of coordinates and is a component of the first feature reported in the URL in the script above.

 [
   16504625.024250001,
   -4372770.7781249993
  ],
  [
   16504645.846749999,
   -4372777.386500001
  ],
  [
   16504664.026874997,
   -4372785.385625001
  ]
 ],
 [
  [
   16504684.332374997,
   -4372794.3222500011
  ],
  [
   16504706.535875,
   -4372804.0945000015
  ],
  [
   16504730.744125001,
   -4372813.5017499998
  ],

Because the script treats the data as a "LineString" different sections of the the same paths are connected by relatively long straight lines. An example of the these erroneous relatively long straight lines are shown in the picture below which is a plot of the features in the layer as interpreted by the script.

Answer 1

The following code will parse an ArcGIS (ESRI) REST MapServer MultiLineString JSON url so that it can be read by the GDAL GeoJSON driver. The code achieves this by constructing a new JSON object and copying the relevant data from the ArcGIS REST MapServer JSON url. This could be easily turned into a function.

import ogr
import urllib, json

url = 'http://maps.six.nsw.gov.au/arcgis/rest/services/sixmaps/LPIMap/MapServer/16/query?geometry=16501408.594,-4372525.989,16523000,-4320000&geometryType=esriGeometryEnvelope&f=pjson&outFields=functionhierarchy,OBJECTID,shape,roadontype,roadnamestring,shape_Length'

response = urllib.urlopen(url)
data = json.loads(response.read())
data1 = {}
data1['type'] = 'FeatureCollection'
#set coordinate reference system
if data[u'spatialReference'][u'wkid'] == 102100:
    data1['crs'] = {}
    data1['crs']['type']='EPSG'
    data1['crs']['properties']={'code': 7483}
else:
    data1['crs'] = data[u'spatialReference']

data1['features'] = []          
for i in range(feat_no):
    data1['features'].insert(i, {})
    data1['features'][i]['type']='Feature'
    data1['features'][i]['geometry']={}
    data1['features'][i]['geometry']['type']='MultiLineString'
    data1['features'][i]['geometry']['coordinates'] = data[u'features'][i][u'geometry'][u'paths']
    data1['features'][i]['properties']={}
    # I don't know how to set attribute data types or lengths
    for item in data[u'features'][i][u'attributes']:
        data1['features'][i]['properties'][item]=data[u'features'][i][u'attributes'][item]

data1 = json.dumps(data1)
ds = ogr.Open(data1)
lyr = ds.GetLayer()

del ds, lyr  

Answer 2

There was indeed a bug in reading ESRI JSON MultiLinestrings with GDAL. It has now corrected in GDAL trunk (version 2.2-dev) with changeset https://trac.osgeo.org/gdal/changeset/34773. No backports have been done to 1.11, 2.0, or 2.1 series.

Despite the problem with multilinestrings GDAL seems to read ESRI JSON quite well. Test with the following JSON

{
 "displayFieldName": "roadnamestring",
 "fieldAliases": {
  "functionhierarchy": "FunctionHierarchy",
  "OBJECTID": "OBJECTID",
  "roadontype": "RoadOnType",
  "roadnamestring": "roadnamestring",
  "shape_Length": "shape_Length"
 },
 "geometryType": "esriGeometryPolyline",
 "spatialReference": {
  "wkid": 3857,
  "latestWkid": 3857
 },
 "fields": [
  {
   "name": "functionhierarchy",
   "type": "esriFieldTypeSmallInteger",
   "alias": "FunctionHierarchy"
  },
  {
   "name": "OBJECTID",
   "type": "esriFieldTypeOID",
   "alias": "OBJECTID"
  },
  {
   "name": "roadontype",
   "type": "esriFieldTypeSmallInteger",
   "alias": "RoadOnType"
  },
  {
   "name": "roadnamestring",
   "type": "esriFieldTypeString",
   "alias": "roadnamestring",
   "length": 80
  },
  {
   "name": "shape_Length",
   "type": "esriFieldTypeDouble",
   "alias": "shape_Length"
  }
 ],
 "features": [
  {
   "attributes": {
    "functionhierarchy": 4,
    "OBJECTID": 2857,
    "roadontype": 1,
    "roadnamestring": "ALPINE WAY",
    "shape_Length": 121053.94010502081
   },
   "geometry": {
    "paths": [
     [
      [
       16490352.71125,
       -4374934.9532499984
      ],
      [
       16490354.657125004,
       -4374949.0618750006
      ],
      [
       16490364.728625,
       -4374975.3704999983
      ],
      [
       16490377.779749997,
       -4374991.6128749996
      ],
      [
       16490395.435874999,
       -4375003.0787499994
      ],
      [
       16490411.941624999,
       -4375010.7230000012
      ]
           ]
          ]
         }
        }
       ]
}

Ogrinfo finds the SRS and attributes:

ogrinfo esritest.json -al -so
INFO: Open of `esritest.json'
      using driver `GeoJSON' successful.

Layer name: OGRGeoJSON
Geometry: Line String
Feature Count: 1
Extent: (16490352.711250, -4375010.723000) - (16490411.941625, -4374934.953250)
Layer SRS WKT:
PROJCS["WGS 84 / Pseudo-Mercator",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",0],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AXIS["X",EAST],
    AXIS["Y",NORTH],
    EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +
x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs"],
    AUTHORITY["EPSG","3857"]]
FID Column = OBJECTID
functionhierarchy: Integer (0.0)
OBJECTID: Integer (0.0)
roadontype: Integer (0.0)
roadnamestring: String (80.0)
shape_Length: Real (0.0)