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Creating an offline sketch polygon map area does not work

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12-18-2024 08:23 AM
doronwen
Frequent Contributor

I'm trying to create offline maps for field crews in an area with no reception.

The area I'm trying to capture is not a perfect rectangular (I'm capturing areas around roads, linear events), so I'm using the "Sketch polygon map area" option to capture my area. 

But each time the results (the offline map) come back as a rectangular shape, with 4 vertices, and not the original shape I drew on the map. See images below.

It appears that the tool picks 4 vertices from the odd rectangular shape I created and extrapolate it to a 4-corner rectangular. 

Is this a bug in Field Maps? Or am I doing something wrong? I'm on enterprise 11.1

Field Maps 01.jpg  Field Maps 02.jpgScreenshot 2024-12-20 at 8.29.32 AM.jpeg.png

 

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KerriRasmussen
Esri Contributor

@doronwen 

You’re very welcome, happy to help. As for your question about cropping the basemap, the tool is “cropping” or reducing the number of tiles included in the package, but in a slightly different way. If I were to create the same area using the rectangle tool verses the sketch polygon tool, the offline area using the sketch polygon tool will be smaller. However, instead of clipping the tiles to the outside of the polygon sketch area, whole tiles that intersect with the polygon at all levels of details are packaged. As you zoom into the map, the areas within the polygon sketch area will have more levels of detail downloaded, showing a clear imagery basemap, while the tiles outside will be more pixilated. The example below shows the areas in the polygon on the right and outside the polygon on the left.

I did check the documentation and we don’t go into much detail on raster/vector tile layers, but I will be recommending an update to make the distinction clearer.

As for adding to the Ideas section, I am a strong advocate for customers adding ideas to the page. However, since the reason for the current functionality has to do with performance, it would seem unlikely for the change to happen. Clipping the tiles required a lot more work on the server side, which slows performance.

IMG_0348.png

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7 Replies
KerriRasmussen
Esri Contributor

Good morning. The issue you are seeing with taking your maps offline using the sketch polygon method is most likely due to the basemap you are using. The map's basemap must be an ArcGIS Online hosted tile layer or a tile layer from an ArcGIS Enterprise 10.7 or later portal. Try switching your basemap and then recreate the offline area with the tile layer basemap and that should do the trick. 

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doronwen
Frequent Contributor

Hi @KerriRasmussen 

The map I'm using is an  ESRI service coming from AGOL that is referenced into our Enterprise portal which is 11.1. 

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KerriRasmussen
Esri Contributor

@doronwen Thank you for the additional information. I've done some digging and this is excepted behavior. When using a raster tile basemap with the sketch polygon tool it will not clip the tiles and will return the whole tile for any tiles that fall within the sketch boundary, giving you the shape you are seeing. 

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doronwen
Frequent Contributor

Thanks for looking into that @KerriRasmussen. this is interesting. why wouldn't the tool crop the basemap? that's defeating the purpose of using the sketch tool to begin with. also, I would expect the sketch tool to provide users a warning saying that this will be the expected results (basemap will not be cropped).

Out of curiosity, is there Esri documentation that explains the reason behind this behavior?

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doronwen
Frequent Contributor

Should I add this to the "ArcGIS Ideas" section?

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KerriRasmussen
Esri Contributor

@doronwen 

You’re very welcome, happy to help. As for your question about cropping the basemap, the tool is “cropping” or reducing the number of tiles included in the package, but in a slightly different way. If I were to create the same area using the rectangle tool verses the sketch polygon tool, the offline area using the sketch polygon tool will be smaller. However, instead of clipping the tiles to the outside of the polygon sketch area, whole tiles that intersect with the polygon at all levels of details are packaged. As you zoom into the map, the areas within the polygon sketch area will have more levels of detail downloaded, showing a clear imagery basemap, while the tiles outside will be more pixilated. The example below shows the areas in the polygon on the right and outside the polygon on the left.

I did check the documentation and we don’t go into much detail on raster/vector tile layers, but I will be recommending an update to make the distinction clearer.

As for adding to the Ideas section, I am a strong advocate for customers adding ideas to the page. However, since the reason for the current functionality has to do with performance, it would seem unlikely for the change to happen. Clipping the tiles required a lot more work on the server side, which slows performance.

IMG_0348.png

doronwen
Frequent Contributor

@KerriRasmussen Thanks for the detailed response.

If I understand you correctly, there isn't a cropping going on, but more like a geoprocessing 'Select by location'.
The area I draw (polygon or sketch) does not crop the imagery pixels but selects the available raster tiles instead. If that's the case, that is a big drawback of the tool that its purpose it to help collect data in the field.
The fact that Esri limits the number of offline maps that can be downloaded (I think it's 16?) and now this raster/sketch issue makes it really difficult to prepare offline areas for field workers in areas where there is not cell reception.

In any case, thank you for looking into this and provided me with all the details. 

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