[OpenLayers-Users] pixel units to lat/lon units & nexrad

[Scott Baker]

Guess I got that one totally wrong (I'm very new to all this)

I had looked at those posts - but they still show just a single TMS 
layer - not TMS and WMS combined. The bit I was looking for was an 
example of using a TMS on top of a WMS layer - for example - say a small 
custom raster map (not of the whole world) split into TMS tiles that 
should sit at a certain spot on a world basemap. I'd still love to see 
an example of that if you know of any.

As for the popper prep of data for serving and mapserver speed - yes the 
data probably could be much better - I'd just doing my best trying to 
learn way more about GIS and these systems then I ever intended to do 
:)  It's all converted to shapefiles and only 2 TIFs - large shapefiles 
are split into tiles, everything has tile indexes, limits for various 
layers by scale, and all the unused data has been stripped out - but I'm 
really just fumbling to make it work - that said there are 27 layers 
(about 8GB) of data I need to combine into a nice map - I was happy I 
got it to work at all :)

PS: Please don't get me wrong - I hope that last email didn't come 
across as being angry or negative about OL or this group (email 
sometimes comes across that way even when not intended) - I was just 
trying to help someone with seemingly the same problem.

There is an immense amount of knowledge built up inside many of the 
people here - I am truly in awe of how much people know about all this 
stuff - I think there are a lot of us just trying to catch up enough to 
get something to work - please bear with our/my ignorance.  For example 
suggesting writing another tool to do something like what gdal2tiles 
does - I wouldn't ever even think of embarking upon a task like that 
until I finally manage, for example, to wrap my head around how a 
bounding box can be specified using metres instead of Lat/Long for units 
(still stumps me - and yes I have read the posts about it)  "@^# it jim, 
I'm a programmer not a cartographer!" ;)

 

Christopher Schmidt wrote:
> On Wed, Jun 04, 2008 at 09:55:40AM -0700, Scott Baker wrote:
>   
>> I was trying to do something similar to this when I first started - I 
>> asked here in the list about it too - but received no response. So I 
>> spent 3 months figuring it out myself... Correct me if I'm wrong, but I 
>> couldn't find any way to use gdal2tiles for anything other then a single 
>> map - always in pixel coordinates and not suitable for any sort of 
>> overlays.
>>     
>
> I think I responded to that claim from another user here:
>
>  http://www.nabble.com/GDAL2Tiles-td16458672.html
>
>  http://openlayers.org/pipermail/users/2008-April/005362.html 
>
>   
>> It's a great method for creating a standalone OL viewer of a raster map 
>> but that's about it.
>>     
>
> I would tend to disagree.
>
>   
>> As soon as you want to get into mixing layers, overlaying stuff - etc... 
>> you will need a mapserver to do it.
>>     
>
> This is definitely not true -- even if you can't use gdal2tiles, you
> could always write another tool that did something similar. 
>
>   
>> I ended up with mapserver running and then implementing tilecache 
>> (mapserver is incredibly slow directly) 
>>     
>
> I doubt this is true. It is more likely that your data is poorly
> prepared for serving dynamically. (Properly preparing data for dynamic
> serving is hard. For vector data, it requires intelligent cartographic
> decisions. For Raster data, it requires effort to be put into ensuring
> that your data is properly overlay-ed, tiled, not-compressed, etc.) 
>
>   
>> then an OL display. The 
>> combination of the three is the only way I found to get nice looking 
>> maps and have floexibility enough to include raster, vector, and public 
>> data in OL.
>>     
>
> Sure, but that's not related to the question at hand. gdal2tiles can't
> draw vector data into tiles, so you'll need to set up a server for that
> part of it.
>
> Regards,
>   

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