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Adding Visual Coordinates Renders Slowly

When adding several hundred coordinates using the visual system, the re-rendering of the map slows to a crawl. It can literally take 5 minutes from the time I select the location on the old map to selecting the location on the new map to finally rerendering the adjusted map.

Pyramid TIFF
15000px x 18000px
1200 Coordinates

  1. What can be done to improve coordinate mapping rendering speed?
  2. Is there an optimal format that would help, other than Pyramid TIFF?
  3. The CPU, GPU, and RAM are barely being utilized. CPU is at 12%, GPU is barely registering any processing. RAM is at 1.7GB for mapTiler Desktop.

I am working on a late 2014 27" iMac Retina, 32GB RAM, and SSD harddrive.

Any suggestions would be greatly appreciated. Thank you!

3 replies

Hi Jiri & Devs:

This is a scanned historical city map, requiring georeferincing points at nearly intersection. It is not at all sufficient to provide only 10 points.

I have recovered the file by reverting back to version 9 of MapTiler, and will upload the file in a few minutes.

Hi Mike,

The slowness of the map is obvious: 1200 GCPs is really redundant. It is not improving the accuracy of the map. 10, max 20 points is more than enough. 

Our recommendation in this case is still the same: use max. 10 - 20 GCPs.

Best regards,

Jiri

Hi Jiri,

I find the immediate dismissal of the requirement to do detailed adjustments for a map a bit surprising. I have uploaded the image yesterday, did you have a chance to look at it? You will notice that with only 10 or 20 reference points, the street intersections do no line up correctly in all places. Thus I need to adjust most intersections.

I'm alarmed that this concern is being dismissed out of hand, and not even try to replicate and understand my concern as posted originally. I am suspecting that MapTiler is artificially throttling performance, because CPU, memory, and hard-disk usage are no where near maximum. If it were an issue regarding the number of reference points, I would expect my CPU (or GPU, depending on rendering technologies used) to be pushed to the max.

Hi Mike,

yes, I downloaded the map and tried to render it. Yes, it is slow and the main MapTiler Desktop developer again confirmed it is slow due to the high number of GCPs. 

His tip how to improve the accuracy of the final map is to position each georeference point as accurate as possible. If it is still not enough accurate, rather move existing georeference points than adding new ones.

That's the maximum we can advise you.

Best regards,

Jiri

Sorry for being so late to respond to this. I was just preparing to upload my file, when I noticed that for some reason all my marker points are missing. I will have to recreate that file, will probably be a few weeks before I can get to it.

Mike, before recreating all 1200 GCPs, think carefully if you really need so many points to georeference the image. As our devs pointed out, 10 points is more than enough to get perfect overlay! 

It would be helpful to know what type of map is being georeferenced (an old scanned map? scale, dpi, etc).

1200 GCPs suggest you have a wrong workflow - usually you need ~10 points with correct SRS to get a perfectly fitting overlay.

- Why do you specify 1200 GCPs?

- Could you please upload us privately the file to https://klokantech.com/upload/?