[Freegis-list] Ideas on best FOSS options

[Artem Pavlenko]

On 6 Feb 2008, at 04:10, John Zastrow wrote:

> Artem Pavlenko wrote:
>>
>> On 4 Feb 2008, at 02:01, John Zastrow wrote:
>>
>>> I need to create an attractive set of static tiles for the USA  
>>> (based on
>>> shapefiles) to populate a web-server-only (e.g., small-footprint,  
>>> not
>>> dynamic, not a real map server) online map to embed in a java-based
>>> application without internet access.
>>>
>>> My first attempt used ArcGIS to render a GeoTIFF of a layout at high
>>> resolution and then passed the image into gdal2tiles.py
>>> (http://www.klokan.cz/projects/gdal2tiles/) (which is EXCELLENT) to
>>> create a shell OpenLayers app that I can customize. This worked  
>>> fine,
>>> except the image quality from ArcGIS was horrible, particularly when
>>> zoomed in (no anti-alias).
>>
>> I don't think your approach will work.  Even if you manage to  
>> create a
>> very large geotiff, re-sampling it to create low resolution tiles
>> would produced anything but nice looking maps. Also, for high zoom
>> levels the image size will blow your memory away. Creating good
>> cartography would most certainly require per zoom level styling.
>>
>>>
>>> I'm a now trying to use mapnik (mapnik.org) to create the same  
>>> image at
>>> higher quality. But I am suffering deeply from an acute lack of
>>> documentation which makes creating the cartography even more painful
>>> (where are recipes, examples, and docs for mapnik?)
>>
>> Have a look at :
>> http://trac.openstreetmap.org/browser/applications/rendering/ 
>> mapnik/generate_tiles.py
>> [1]
>> This script generates tiles with all styles and data defined in :
>> http://trac.openstreetmap.org/browser/applications/rendering/ 
>> mapnik/osm.xml
>>
>>
>>>
>>> Is there something else that I can use to create the tiles needed  
>>> for
>>> the OpenLayers app?
>>
>> I suggest you read OpenLayers docs.
>>
>>> Or is there an easier tool for creating a high-res,
>>> high-quality georeferenced image that can be used by  
>>> gdal2tiles.py? Any
>>> thoughts would be greatly appreciated.
>>
>> I'm not familiar with gdal2tiles.py but as I mentioned above,
>> re-sampling vector maps won't produce high-res, high-quality tiles
>> (assuming this is what you're trying to achieve).  You might try
>> creating two layers : chop your raster data with gdal2tiles.py and
>> create transparent overlay tiles using Mapnik. Also, Mapnik supports
>> gdal raster directly and you can generate high quality tiles with
>> raster and vector combined. see [1]
>>
>> HTH
>> Artem
> Ok, you lost me a little with your last note (I agree, I'd like to  
> weave
> together at least two zoom levels into a static tile set). Are you
> saying that Mapnik can import the newly cut tiles and set transparency
> (perhaps based on a color)?

No.

> Can you elaborate on what I would do with
> Mapnik's support for GDAL rasters?

Mapnik can generate tiles from vector and raster data sources  
(including gdal raster).  gdal2tiles.py is for *raster only* tiles.

> If [1] was a link it did not come
> through in the email.

[1] is a link to Python script which you can use as a starting point.  
Here it is again:

http://trac.openstreetmap.org/browser/applications/rendering/mapnik/ 
generate_tiles.py


>
> Thanks.

Cheers
Artem
>
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