Viewing Custom Maps' KMZ files in a browser - valid? rotation?

[Gwayne Stern]

I discovered by accident that if I double click a KMZ file that I made on my Android using my PC's browser, it opens and shows my JPEG image overlaid over a Google map of that location, which is cool, and gives a nice overview of how the overlaid images will work together in the Custom Maps app.

However, when making a new KMZ with an updated image that does not have North oriented at the top, and opening the resulting KMZ file in my browser, it showed the JPG image overlaid on a Google map, but not rotated, so the image does not align with the Google map, except for one of the two tie points.  I tried over and over again, making sure I rotated one or both tie points in the app (which would seem technically unnecessary to me anyway, except that it helps us humans line up the images by eye much more easily), but the resulting KMZ always showed the JPG without it being rotated to match the Google map, when viewed on my PC browser.

This raised several questions for me:

*) Will my latest Custom Map work correctly?  I will have to drive an hour to get there and find out; I hope I don't find that it does not work when I get there.  Seeing it incorrectly overlaid in my browser raises some doubts...

*) Why is it that whenever I go back and edit a tie point in this map in the Custom Maps app, it displays without the rotation, even though I have tried rotating, Preview, and Save over and over again?  Is that normal, the rotation is not saved, since it is really not needed, once two or more tie points are established??

*) Is it normal for the JPG not to appear rotated when viewing the KMZ in a browser?  Is opening the KMZ in a PC browser even a valid thing to do?  Can it be used to verify (roughly) That the overlay lines up with the Google map?

By the way, I think this app is the greatest thing to ever happen to my Android phone!

[Gwayne Stern]

EDIT:  To clarify, the map does preview correctly in the Custom Maps app, properly rotated, and both tie points lining up.  Of course, I can't fully verify proper operation without being on site, but I suspect it will work fine, since I have not read about this issue for anyone else.  Regardless, I would be interested to hear the developer's standpoint on the observations of viewing Custom Maps' KMZ files in a browser, both those made from images WITH North at the top, and those without (and perhaps why/how it chooses to depict one tie point correctly, but not the other in the case of the latter (perhaps it is the first tie point created))?  Please pardon me in advance if I have ventured too far into the arena of the irrelevant, it's just that I am truly fascinated by this app, from a lay viewpoint.

[Marko Teittinen]

These are totally understandable questions that you pose in your emails. I'll try to answer and explain below.

First, your map will work correctly in Custom Maps. Custom Maps always displays the map image in its "native" orientation, as rotated bitmaps become relatively blurry on lower resolution screens. I guess very high resolution maps (>16mpix) on very high resolution screens (>300 dpi) the rotated bitmap images might be legible, but by keeping the actual image orientation maintains the best map image quality regardless. In the early days of the app I played around with rotating the map images to north up always, but I decided it wasn't worth it with the degraded image quality.

Second, the orientation is saved in a matrix that converts your geo location to map image coordinates and vice versa. It is just that Custom Maps always display images without rotation.

Third, the kmz file should display correctly oriented when opened in Google Earth (at least on desktop). Google's support for image overlays on the web map products varies, and many of the newer versions may not support all features of image overlays. If you use only two tiepoints, the resulting kmz file should contain the simplest possible markup for a rotated image overlay, but it is possible that the image overlays are not always properly rotated when displayed in Google's web pages. If you use more than two tiepoints, then the resulting markup is more complicated (but still valid kml) and the image overlay is even less likely to dislay correctly in other tools that do not support all aspects of kml image overlays.

The best way to get "independent" validation of kmz file created in Custom Maps is to open it in the desktop version of Google Earth. My understanding is that Google Earth has the most complete kmz/kml parser of Google products.

I hope this helps. Feel free to ask more questions if I missed answering something or if my explanation was not clear.

Marko Teittinen

On Tue, Jan 28, 2014 at 10:08 PM, Gwayne Stern <accu...@gmail.com> wrote:

EDIT:  To clarify, the map does preview correctly in the Custom Maps app, properly rotated, and both tie points lining up.  Of course, I can't fully verify proper operation without being on site, but I suspect it will work fine, since I have not read about this issue for anyone else.  Regardless, I would be interested to hear the developer's standpoint on the observations of viewing Custom Maps' KMZ files in a browser, both those made from images WITH North at the top, and those without (and perhaps why/how it chooses to depict one tie point correctly, but not the other in the case of the latter (perhaps it is the first tie point created))?  Please pardon me in advance if I have ventured too far into the arena of the irrelevant, it's just that I am truly fascinated by this app, from a lay viewpoint.

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[Gwayne Stern]

Marko:

Thank for your prompt and thorough response.  Your answers make sense, though they touch on a few topics a bit too technical for me to understand.  I am reassured to know my Custom Map will work when I get on site (as also shown by Previewing it in Custom Maps).

I am not at a place to try opening my Custom Maps KMZ files in the full Google Earth application (as opposed to in a browser) right now (to see if it displays them correctly rotated), but I will do so and re-post here when I have the time.  It will be nice to know there is a way to view and present the Custom Map KMZ on a PC, if it works in Google Earth.

Your active support of this app makes it even more valuable to all us users.   Thanks again for your prompt response!

 - G

[AccuSpeed]

Success!  The KMZ file created in Custom Maps from a JPG that does not have North at the top does indeed display correctly rotated and overlaid in Google Earth!

Example:

older file that has North at the top: https://drive.google.com/file/d/0B9xiEQ7JGRNzZ290MUNUNC1Zb25FSW5Oa210OXYweHZVd3A0/edit?usp=sharing

newer file that does NOT have North at the top: https://drive.google.com/file/d/0B9xiEQ7JGRNzUGYtcTNWVS1XckFsT2ZuRG4yWXdhcVdxYjI0/edit?usp=sharing

If you are running Chrome, these will open right up when you click them (I hope), and you will see (at least if your platform matches mine closely enough) that one looks right, and one looks wrong.

But if you open them in Google, Earth, they both look right!

Thanks, Marko, for explaining why this is, assuring my confidence in rotated maps I create in advance, and pointing out that Google Earth is the best way to preview/validate your Custom Maps KMZ files.  Plus it is awesome bringing them up on a large screen and having 3D viewing control!