Cesium reprojection for UTM tileset.

[arbit...@gmail.com]

Hi guys,

Apologies in advance for the long post and a bit of rambling. I know that this might be a duplicate topic but I haven't been able to find a consolidated answer on the forums.

I'm using a UTM-K tileset (http://www.osgeo.kr/17 at https://epsg.io/5179) that uses a Korean standard (http://map.naver.com).

The tiles were premade by the client and I would prefer to use the tiles as is without reprojecting them from a WMS/TMS server.

Which I assume to mean that I have to either reproject the globe from cesium or change the tile calculation.

On 2 dimensional maps I've tried using proj4js with some success, but working with ol3-cesium puts too much things to tinker with and the default API given by ol3-cesium seems to be a bit limited.

On cesium I've tried editing the buildImageUrl() function. When changing the buildImageUrl() function I've noticed that I can get very close, but not to the correct location, and that if I tried going closer to the target location I'd have to move the tile by half a unit or so, which leads me to think that manually changing the tile requests was a faulty idea on my part.

Some of the concerns I have when working on this are:
1. the tiles provided start at level 6 instead of 0. This means that when I load the globe it attempts to load all 4096 tiles at once. I assume I can bypass this by using the camera flyto() and then adding in the imagery layer after the flyto() even, but since I haven't got the correct projection I haven't tested this out yet.
2. if I reproject the globe instead of creating a custom tile calculator, if I place terrain information that uses EPSG:4326 it would not match up with the provided image. Can anyone confirm or deny this?
3. I'm new to the whole GIS thing, so this one seems like a silly question, would Korea be usually represented by UTM51N or UTM52N? since it lies across both units, and would the other letters in the UTM scheme be used? such as S or R for Korea?

Thank you taking your time to read through this.
If further details are needed please let me know.

Thanks and Regards,
Sangkeun Kim

[arbit...@gmail.com]

Sangkeun here again, what I've attempted at the moment:

I've been trying to backtrack how to move the X and Y co-ordinates from the Imagery Provider. However that seems rather unfruitful at the moment, as I dig deeper it seems the cleaner way would be to create a new ellipsoid with the correct x and y starting points.

So the main problem is that if I use the UTM projection to put the map imagery and use EPSG to put the terrain, the two projections will not match up. Does anyone have a solution for that?

Alternatively, I've been trying to find a premade UTM projection plugin for Cesium but there does not seem to be one. Is using GDAL on the premade tiles the only way to go about this?

[Michael Gevlich]

Hi, why dont you make a reprojection UTM tiles to the Web Mercator?

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пятница, 26 февраля 2016 г., 16:17:06 UTC+3 пользователь arbit...@gmail.com написал:

[arbit...@gmail.com]

Thanks for taking the time to reply. Unfortunately the tiles are not made by us and the updates are provided by a third party in the form of UTM tiles. That means that unless we create a UTM projection on Cesium, we would have to create a reprojected tileset every time the map is updated.

Unless you'd meant why I don't reproject to Web Mercator withing Cesium, which I'm trying to ask if there's a clean way.

[Hannah Pinkos]

Hello Sangkeun,

Sorry, there isn't anything built into Cesium for handling UTM tiles.  You will have to implement the projection yourself.

Best,

Hannah

[Sangkeun Kim]

Thanks for taking your time to reply Hannah. Firstly,  thanks for confirming that cesium doesn't have UTM built in. The official checklist is from 2013 and i wasn't too sure. I'm looking for problems and solutions that might arise from a custom implementation and to see if there are third party plugins or examples.

Again thanks for your confirmation. I really appreciate it.

[Hannah Pinkos]

No problem, sorry for not answering your question sooner.

I don't know of any third party plugins or anything.

This isn't an area of the code I'm very familiar with, so I don't have any suggestions for doing your own implementation.  Hopefully someone else will be able to give you some information.

-Hannah

[Sangkeun Kim]

Haha, fair enough. If i succeed in a clean implementation I'll let you know.

[christop...@gmail.com]

Hi!
I'm having the same problem. I want to use OL3-Cesium to display a 2,5D (Columbus) view of UTM tiles (EPSG:326XX) delivered by GeoServer. But I don't want to reproject to EPSG:4326 from GeoServer as I have to stick to native format. Seemingly, Cesium doesn't take advantage of proj4js like OpenLayers does.

Kim, did you find a solution to your problem? Adapting existing code is not a too tricky task?

Thanks.
Christophe