topic Re: Google Map Scales query in ArcGIS Enterprise Questions

Google Map Scales query

DavidRowe1 — Mon, 06 Feb 2017 02:24:59 GMT

Hi there, I'm setting up cached map services of some aerial imagery datasets and I'd like to use the Google/AGOL standard cache levels/scales as defined in the default caching scheme provided in ArcGIS Desktop 10.3. Unfortunately these scales only have a maximum zoom scale of 1:1128 and I'd like to include a 1:500 scale, and I guess

I can add my own custom scale level but I'm a little puzzled though because when I look at the scaling in Google Maps I can clearly see that it zooms to a larger scale than 1:1128. Converting the scale bar gives me a scale of about 1:175 ie the scale bar measures '2.85cm for 5m'.

So am I missing something here, or making an assumption about what Google terms as 'map scale' ?

Cheers

Dave

Re: Google Map Scales query

FC_Basson — Mon, 06 Feb 2017 05:53:39 GMT

I think Google only caches to a scale of 1:1128 and you'll see that after 1:1128 scale the images start pixelating. Check out this tutorial on how to extend your AGOL scale levels

Re: Google Map Scales query

DavidRowe1 — Mon, 06 Feb 2017 06:08:50 GMT

Hi, thanks for getting back to me. Makes sense I guess but that would suggest there should be more than the so-called 19 or 20 published scales for Google Maps. I'm not sure if it's different for our part of the world (Australia), but we only have 19 zoom levels. If as you say, they're only the cached scales then the additional scales would be something like 1:564, 1:282 & 1:141 unless they abandon the base 2 scheme that's used for the existing scales.

Cheers

Dave

Re: Google Map Scales query

FC_Basson — Mon, 06 Feb 2017 06:20:48 GMT

Hi David, I reckon the additional scales as mentioned in the article are just for extending your own imagery cache scales at the same scale level factor as the Google scales, which are the default levels for AGOL and the JS API. Google only provides their cached imagery up to level 19, from there on it is just blowing up the picture. See the Map constructor details with regards to LOD for the 3.19 API (Map | API Reference | ArcGIS API for JavaScript 3.19 )