This post will demonstrate how the user can ensure the layers he or she digitizes on internet base maps in Esri Arcmap align well on other internet base maps like google and OSM and vice versa.
We will digitize features on an ESRI base map, convert them to shapefiles in Arcmap 10.4 and load this shapefile for use on a google map in QGIS desktop. Our primary target is to ensure the features align properly on the base map both in Arcmap and QGIS. Note that ArcMap will be using the ESRI satellite basemap while QGIS will use google satellite.
1. Launch your ArcMap. Open a blank map and right click on Layers and select Properties from the dropdown list.
We want to set the Data Frame properties to the appropriate Coordinate Reference System (CRS).
2. In the Data Frame Properties window, click on Coordinate System and input 3857. 3857 is the SRID that is consistent with ESRI Base maps. Click OK to save the changes.
3. Now let us add the base map. Click on the Add button icon – Add Basemap (ArcGIS must be connected to online resources).
4. We select the Imagery option for a base map. Click Add to download the map.
6. Next we create a shapefile. Go to the Catalog and select our working folder – New – Shapefile
7. The Create New Shapefile window will open. Give a name to the shapefile. Click on Edit to assign the appropriate CRS to the shapefile.
8. Assign the same CRS as the Esri basemap and Data Frame. Click Ok and the new shapefile-satfield- will be added to the Layer window.
9. We digitize a polygon feature on the base map and save it in the satfield shapefile.
Let us now go to QGIS to see if the newly created shapefile – satfield will align on a google base map there.
10. Launch your QGIS Desktop and Go to Web – OpenLayers plugin – Google maps – Google Satellite. Note that user will have to enter a google api key before you can have access to the maps from google in QGIS. This simply means getting an API key from google maps api and logging it in using the ‘Set API key’ option.
11. Use the browser panel to navigate to where the shapefile=satfield is located. Double click on it to add it to the Layer window.
12. Right Click on the layer and select Zoom to Layer.
13. Viola! The layer seats exactly the same location as it was on the ESRI basemap in ArcMap.
14. Now we will create a shapefile and digitize a line feature on the google base map here in QGIS and see whether it will also align when placed on the ESRI basemap in ArcMap. Click on Layer – Create Layer – New Shapefile Layer
15. In the New Shapefile Layer window, we will create a line feature. Make sure the CRS is set to 3857 which corresponds to that of the google basemap. Click OK
16. We name the shapefile- satline and save it in our working folder.
17. We start to edit and create a feature( follow red line arrow on the screenshot below).
18. Now we go back to ArcMap. Open the catalog and refresh the working folder.
Navigate to where the shapefile-satline is and add to the map.
19. Viola! the line feature created from the google map in QGIS fits snugly into the same geographical location on the ESRI basemap.( Follow green arrow line on the screenshot below).
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