GUI based Photorealistic Condor Scenery Tutorial - draft

Everything related to creation of new sceneries for Condor...

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luisbriones
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby luisbriones » Thu May 04, 2017 2:30 am

tberry wrote: Are you SURE that you didn't accidentally use Lurik's calibration points in the flight planner example you posted?

Yes, I'm sure. I checked it a lot. If I use your data I have wrong distance. When I put the Lurik data the distance are ok.
In both case I work with a SRTM data that I didn't convert to UTM in 3DEM. Maybe the pixel size must be put for the user

tberry wrote:Out of curiousity, what technique are you using to cut the imagery tiles and where are you getting the numbers to cut them from?


I use SAS.Planet program. With it you download the image to buffer and then you can make it. One option is fragment that image in many row and columns. It's work very well to wgs84, but the program don't has UTM projection as option to save the file. Maybe we may ask to programer if can add this feature in the future.

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Jan Oorthuijsen
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby Jan Oorthuijsen » Thu May 04, 2017 1:56 pm

My Enlish is not good to proper explenation.
Last edited by Jan Oorthuijsen on Thu May 04, 2017 8:13 pm, edited 3 times in total.
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luisbriones
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby luisbriones » Thu May 04, 2017 2:32 pm

Thanks for the info.

Maybe this is not the accurate procedure to obtain an scenery.

By the way, I found the way to follow the P. Strzelec using QGIS with my images obtained from SAS.Planet software. It's works in low definition. I wrote a tutorial and I follow it to obtain a High Definition. I need make some changes of it to adapt to big files procedures.

SAS.Planet permit obtain worldwide geotiff images. There are not in UTM, but I wrote asking about the possibility of add this feature in a future.

PS: I convert files (or other process) using batch. Here is better explains
https://www.youtube.com/watch?v=TIaca4T9hQs

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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby tberry » Fri May 05, 2017 12:47 am

I stopped following this tutorial because the longtitude lines go towards the poles and the distance in meters decreases.
I have pointed that out here, but it seems that this error is still being made.


This error exists no matter how you go about generating the scenery and cannot be corrected. The reason for this is that, as you point out, the globe cannot be defined as a square grid.

However, Condor requires that you define your scenery as a square grid. In lower latitudes, this is not as apparent as at higher latitudes. In addition, using 3DEM, as the manual instructs, and saving as a Terrain Matrix yields a format that is WGS84, also known as EPSG:4326. This WGS84/EPSG:4326 projection is what is required for imagery tile output for Condor. The disadvantage of WGS84/EPSG:4326 is the distortion at the poles.

In the diagram below, you see a UTM grid in lat/lon on the left. The Condor scenery grid is on the right and it is represented only by pixels. What the calibration file does is provide a direct mapping of pixels to lat/lon. Note that it is a BACKWARDS mapping of pixels with the orgin (0,0) being in the lower right and increasing as you go to the LEFT. Note the line 0,0,-40.56582186,-66.18171986 tells Condor that the lower left corner (the orgin) is at -40.5, -66.1 lat/lon. Likewise, the upper left is 230400,322560,-37.6936068,-68.90715888. That is pixels 230400 and 322560 of the SRTM grid. The calibration points file provides a grid of these lat/lon and pixel locations to Condor and I presume it interpolates between them.

You can see from this that Condor does not know anything about lat/lon at all. It only knows pixels, which are square. This means no matter how you calibrate that there is distortion in the imagery and terrain. However, it is spread over a very large space and isn't really noticeable.

Capture.JPG


UTM uses varying references in an attempt to more closely match the shape of a globe, thus the necessity for different zones. This makes it impossible build a Condor scenery that spans a UTM zone. Using WGS84/EPSG:4326, there is no zone issue.

Maybe this is not the accurate procedure to obtain an scenery.

I'm still not sure how to discover the issue. Did you follow the whole tutorial and then find the distance error? Even with inaccurate calibration points, if you have lat/lon for your airport and your wp it seems like Condor should calculate the distance properly.
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luisbriones
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby luisbriones » Fri May 05, 2017 5:48 am

tberry wrote:This error exists no matter how you go about generating the scenery and cannot be corrected. The reason for this is that, as you point out, the globe cannot be defined as a square grid.

However, Condor requires that you define your scenery as a square grid. In lower latitudes, this is not as apparent as at higher latitudes. In addition, using 3DEM, as the manual instructs, and saving as a Terrain Matrix yields a format that is WGS84, also known as EPSG:4326. This WGS84/EPSG:4326 projection is what is required for imagery tile output for Condor. The disadvantage of WGS84/EPSG:4326 is the distortion at the poles.

In the diagram below, you see a UTM grid in lat/lon on the left. The Condor scenery grid is on the right and it is represented only by pixels. What the calibration file does is provide a direct mapping of pixels to lat/lon. Note that it is a BACKWARDS mapping of pixels with the orgin (0,0) being in the lower right and increasing as you go to the LEFT. Note the line 0,0,-40.56582186,-66.18171986 tells Condor that the lower left corner (the orgin) is at -40.5, -66.1 lat/lon. Likewise, the upper left is 230400,322560,-37.6936068,-68.90715888. That is pixels 230400 and 322560 of the SRTM grid. The calibration points file provides a grid of these lat/lon and pixel locations to Condor and I presume it interpolates between them.

You can see from this that Condor does not know anything about lat/lon at all. It only knows pixels, which are square. This means no matter how you calibrate that there is distortion in the imagery and terrain. However, it is spread over a very large space and isn't really noticeable.


UTM uses varying references in an attempt to more closely match the shape of a globe, thus the necessity for different zones. This makes it impossible build a Condor scenery that spans a UTM zone. Using WGS84/EPSG:4326, there is no zone issue.


I have some dudes about that. Not about your logic, that it's fine. But with the way that condor use the data. If you check my image with calibration points you must see that the point of your row and columns are paralell in WGS84 (Blue). The top red points are closer than the botton points. If you change to see in UTM coordinates, the full grid of red points are paralell and your botton points are closer than the top points. In this way, using UTM projection you have something closer to a square.

tberry wrote:I'm still not sure how to discover the issue. Did you follow the whole tutorial and then find the distance error? Even with inaccurate calibration points, if you have lat/lon for your airport and your wp it seems like Condor should calculate the distance properly.


In some place I read that Condor no use coordinates to calculate distance and speed. Convert coordinates to pixels and use that. That sound logic with our problem. Your grid is more thin that other. If Condor expand in any way that grid the distance are bigger than real.

I think that I followed your tutorial well, but this thays I made a lot trials and errors. Perhaps I forget something.

Maybe, if you have time, the better solution is that you try to make an scenery with my data. Not full scenary, but until make a ghost scenery.
You have my screens captures of your spreadsheet.
My airport (center) is SAHR 39ºS, 67º 37.2'W (-39º, -67.62º) 09-27, 2156x45, 275m heigth. The wp if 39º 5.133'S, 67º 2.617'W

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Jan Oorthuijsen
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby Jan Oorthuijsen » Fri May 05, 2017 12:27 pm

Hi Luis

That I referred to pages 3 and 4 was not to point you to a solution, but to indicate that something was wrong in the way of working with the spreadsheed.
I think you can not work with the input of degrees for Condor.

This because a callibration list was generated with repeated latitude and longitude degrees. And a major deviation in the west-east direction.

I assumed that this problem came back in your question.
Also there was no convertion to the correct UTM zone. Here I was completely stuck,
I knew something was wrong but did not onderstand what.

Condor works with UTM coordinates to allow a square projection (HDR file x-y coordinates + and - 45 meters).
This explains that in Condor after callibration, the coordination points all give a different value in latitude and longtitude.

After that, just worked again with Condor3 dem according to the CST tutorial and calibrated with Luric's callibrator tool. As you indicate at the beginning of your new tutorial.
I only use the intersections of the Terragen tiles to check the correctness of the callibration with the online UTM > dec. degrees conversion.

I have been playing for ten years now with scenery making and texturing ,but can not releas them (copy rights)
My last year (with no copyrights) released Taupo NewZeland scenery looks ok.

I will follow your new topic to learn more about Qgis


(translated with Google)

Grtz Jan
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luisbriones
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby luisbriones » Fri May 05, 2017 4:35 pm

Jan Oorthuijsen wrote:Hi Luis

That I referred to pages 3 and 4 was not to point you to a solution, but to indicate that something was wrong in the way of working with the spreadsheed.
I think you can not work with the input of degrees for Condor.

This because a callibration list was generated with repeated latitude and longitude degrees. And a major deviation in the west-east direction.

I assumed that this problem came back in your question.
Also there was no convertion to the correct UTM zone. Here I was completely stuck,
I knew something was wrong but did not onderstand what.

Condor works with UTM coordinates to allow a square projection (HDR file x-y coordinates + and - 45 meters).
This explains that in Condor after callibration, the coordination points all give a different value in latitude and longtitude.

After that, just worked again with Condor3 dem according to the CST tutorial and calibrated with Luric's callibrator tool. As you indicate at the beginning of your new tutorial.
I only use the intersections of the Terragen tiles to check the correctness of the callibration with the online UTM > dec. degrees conversion.


Tom use a parallel grid of degrees.The east-west distance in meters between points is greater in north than the south. If we look at the grid in UTM coordinates it is clearly seen.

comparacion.jpg

Maybe in some point there no are differences, but if Condor use UTM we are in throubles as you noted time ago.

Jan Oorthuijsen wrote:I have been playing for ten years now with scenery making and texturing ,but can not releas them (copy rights)
My last year (with no copyrights) released Taupo NewZeland scenery looks ok.


I'll bother you in my next step with the scenery!!! :-)

My scenery only pretend be a training place. It's better to fly in know places.

Jan Oorthuijsen wrote:I will follow your new topic to learn more about Qgis


(translated with Google)

Grtz Jan


You chose a bad teacher!

All the merit is to Tom. He introduce me in QGIS and teach me how to use it, in his tutorial. I only adapted his procedures to my troubles.

Regards,

Luis
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby EDB » Fri May 05, 2017 6:09 pm

Just check the hdr file for the correct WGS 84 / UTM zone Target Projection. North or South.
Definitely not EPSG:4326. EPSG:4326 is a Geographic Projection (or Plate Carrée).

WGS84 is the Geodetic Datum used. It is the Coordinate System used to define the shape of the earth. WGS84 uses an ellipsoid.

The UTM zone used depends on where you are on the map surface (earth). The advantage of the UTM projection used is that UTM provides a constant distance relationship anywhere on the map. By using the north and south projection, Condor knows the angle of the earth surface to the sun.

Lurik's Calibration Points are correct.
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Jan Oorthuijsen
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby Jan Oorthuijsen » Sat May 06, 2017 6:36 pm

Thanks for support Erwin.
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luisbriones
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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby luisbriones » Sun May 07, 2017 2:15 am

Thanks for the data!!!

Anyway Tom tutorial have a lot of information very useful

I use that in my tutorial:

http://forum.condorsoaring.com/viewtopic.php?f=3&t=17414&p=151043#p151043

Regards,

Luis

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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby storman747 » Mon Jul 03, 2017 2:46 pm

Not sure you still monitor this, but I could not find your spreadsheet on google sheets

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Re: GUI based Photorealistic Condor Scenery Tutorial - draft

Postby tberry » Mon Jul 10, 2017 11:49 pm

I just checked and it is still there. You click the link and then select "Use Template".

Note that the previous discussion on this thread concerns an issue with the calibration points. I have not resolved that, so if you follow my tutorial all of the lat/lon line up with the imagery but the distances are off by a bit. Until I bite the bullet and do some UTM math with Google Sheets, that will remain an issue.


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