topic Re: Python API project in Python Questions

Python API project

MeToo2 — Mon, 19 Jul 2021 07:14:38 GMT

Could someone please provide an example of how to use this python function. I am unable to get it to work with a transformation. Ideally from Web Mercator to GDA lat long, Web Mercator to WGS84 lat long and Web Mercator to GDA94 MGA56

transformations = geometry.find_transformation(
in_sr=from_SR,
out_sr=toSR,
#extent_of_interest=self.in_extent
)

result = geometry.project(geometries = input_geom, in_sr = from_SR, out_sr = toSR, transform = transformations)

toSR= '4326' #WGS84 or
toSR= '28356' #MGA 56

from_SR comes from the data and is

spatialReference': {'wkid': 102100, 'latestWkid': 3857} I plug in 3857

Re: Python API project

Tim_McGinnes — Mon, 19 Jul 2021 08:47:10 GMT

So the first issue is that you should provide wkid's as integers not strings and the second is that find_transformation returns a list of transforms in JSON, but the project function just wants the wkid for the transform.

Here's some code with outputs showing all the projections you were after. It's a bit more complicated than it needs to be because it is getting the transformation using the from and to SR, then programatically extracting the wkid for the transform. It's way easier just to have a cheatsheet with all your wkid's and directly enter the ones you need.

from arcgis.gis import GIS from arcgis.geometry import Point, project, find_transformation gis = GIS('home') #Create a point in web mercator coordinates ptwebm = Point({"x" : 17041106.13569748, "y" : -3183137.706970891}) srwebm = 3857 #Project point from Web Mercator to WGS84 (no transformation required) srout = 4326 result = project(geometries = [ptwebm], in_sr = srwebm, out_sr = srout) print("Projected Point: " + str(result))

Projected Point: [{'x': 153.08286100000004, 'y': -27.476550999999997, 'spatialReference': {'wkid': 4326, 'latestWkid': 4326}}]

#Project point from Web Mercator to GDA94 srout = 4283 transforms=find_transformation(in_sr = srwebm, out_sr = srout) print("Transforms: " + str(transforms)) srtransform=transforms['transformations'][0]['geoTransforms'][0]['latestWkid'] print("Selected Transform Wkid: " + str(srtransform)) result = project(geometries = [ptwebm], in_sr = srwebm, out_sr = srout, transformation = srtransform) print("Projected Point: " + str(result))

Transforms: {'transformations': [{'geoTransforms': [{'wkid': 8050, 'latestWkid': 1150, 'transformForward': False, 'name': 'GDA_1994_To_WGS_1984'}]}]}

Selected Transform Wkid: 1150

Projected Point: [{'x': 153.08286100000004, 'y': -27.476550999227037, 'spatialReference': {'wkid': 4283, 'latestWkid': 4283}}]

#Project point from Web Mercator to MGA Zone 56 srout = 28356 transforms=find_transformation(in_sr = srwebm, out_sr = srout) print("Transforms: " + str(transforms)) srtransform=transforms['transformations'][0]['geoTransforms'][0]['latestWkid'] print("Selected Transform Wkid: " + str(srtransform)) result = project(geometries = [ptwebm], in_sr = srwebm, out_sr = srout, transformation = srtransform) print("Projected Point: " + str(result))

Transforms: {'transformations': [{'geoTransforms': [{'wkid': 8050, 'latestWkid': 1150, 'transformForward': False, 'name': 'GDA_1994_To_WGS_1984'}]}]}

Selected Transform Wkid: 1150

Projected Point: [{'x': 508186.1329199932, 'y': 6960777.826612913, 'spatialReference': {'wkid': 28356, 'latestWkid': 28356}}]

Re: Python API project

HamishMorton — Mon, 19 Jul 2021 10:23:13 GMT

Hi,

Does the following help at all?

from arcgis import geometry from arcgis.gis import GIS gis = GIS("home") point = [{"x": 12797393.0236, "y": -3693437.2067}, {"x": 12303304.0728, "y": -3681207.2822}] transformations_list = geometry.find_transformation(in_sr = 102100, out_sr = 28356) print(transformations_list) selected_transform = transformations_list['transformations'][0]['geoTransforms'][0]['wkid'] result = geometry.project(geometries = point, in_sr = 102100, out_sr = 28356, transformation = selected_transform) print(result)

Re: Python API project

MeToo2 — Mon, 26 Jul 2021 06:10:56 GMT

Hi Hamish, thanks for your response. setting out the selected_transformation was a great help. Also clouding matters was a weird corruption error for my global constant for srout (in my code). This initially this was a string and I swear blind was working previously. I changed this to a int (as you had it in your code, but was still being corrupted by time of use). I had to cast this as an int in my function and it now works.