mobile and gis dev notes » openlayers

Using GDALWARP to reproject raster that will fit with Google Satellite

rupert — Tue, 29 Jul 2008 12:48:21 +0000

Just a couple of notes to onself using gdal: Use gdalwarp to reproject your GeoTIFF files! I wanted to use my own satellite images acquired from GeoEye, however, on some areas I wanted to use google sat images as well since I don’t have the coverage. In order to do so, I need to reproject the sat images to 900913. Note you need to specify this in your epsg file in my previous post.

rupert:beijing_900913_satellite rupert$ gdalinfo Mosaic_RGB.tif
Driver: GTiff/GeoTIFF
Files: Mosaic_RGB.tif
Size is 4248, 4553
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (116.291476140000000,40.025198500000002)
Pixel Size = (0.000046860000000,-0.000035970000000)
Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_XRESOLUTION=100
  TIFFTAG_YRESOLUTION=100
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  ( 116.2914761,  40.0251985) (116d17'29.31"E, 40d 1'30.71"N)
Lower Left  ( 116.2914761,  39.8614271) (116d17'29.31"E, 39d51'41.14"N)
Upper Right ( 116.4905374,  40.0251985) (116d29'25.93"E, 40d 1'30.71"N)
Lower Right ( 116.4905374,  39.8614271) (116d29'25.93"E, 39d51'41.14"N)
Center      ( 116.3910068,  39.9433128) (116d23'27.62"E, 39d56'35.93"N)
Band 1 Block=4248x1 Type=Byte, ColorInterp=Red
Band 2 Block=4248x1 Type=Byte, ColorInterp=Green
Band 3 Block=4248x1 Type=Byte, ColorInterp=Blue

rupert:beijing_900913_satellite rupert$ gdalwarp -s_srs epsg:4326 -t_srs epsg:900913 Mosaic_RGB.tif sat_4m_rgb.tif
Creating output file that is 4245P x 4556L.
Processing input file Mosaic_RGB.tif.
0...10...20...30...40...50...60...70...80...90...100 - done.

rupert:beijing_900913_satellite rupert$ gdalinfo sat_4m_rgb.tif
Driver: GTiff/GeoTIFF
Files: sat_4m_rgb.tif
Size is 4245, 4556
Coordinate System is:
PROJCS["Google Maps Global Mercator",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.2572235630016,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",0],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]
Origin = (12945507.907502911984921,4869604.732793668285012)
Pixel Size = (5.219801430503303,-5.219801430503303)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (12945507.908, 4869604.733) (116d17'29.31"E, 40d12'53.10"N)
Lower Left  (12945507.908, 4845823.317) (116d17'29.31"E, 40d 3'2.78"N)
Upper Right (12967665.965, 4869604.733) (116d29'25.89"E, 40d12'53.10"N)
Lower Right (12967665.965, 4845823.317) (116d29'25.89"E, 40d 3'2.78"N)
Center      (12956586.936, 4857714.025) (116d23'27.60"E, 40d 7'58.12"N)
Band 1 Block=4245x1 Type=Byte, ColorInterp=Red
Band 2 Block=4245x1 Type=Byte, ColorInterp=Green
Band 3 Block=4245x1 Type=Byte, ColorInterp=Blue

Using TileCache, OpenLayers, Mapserver for Projection 900913

rupert — Tue, 08 Apr 2008 01:50:12 +0000

I had a few problems with TileCache the other week which I am eager to blog about, since I knew for sure that later on, I might encounter the same. I don’t have the exact errors with me right now, so I’m jotting this down from my head…

Classic Resolutions problem. Use extent_type=loose
Can not set image type

UPDATED (JAN 11, 2010): Classic Resolutions problem:

How are resolutions calculated? Assuming we have:

Original:
Lower Left (LL) or minx, miny: 12453557, -5434940
Upper Right (UR) or max, maxy: 16980842, -1180729

maxResolution = (max – minx)/tilesize = (16980842 – 12453557)/512 = 8842.353
where tilesize = 512.

Therefore, we can set/guess for max so that we have maxResolution as a whole number.

Adjusted:
minx, miny: 12453557, -5434940
maxx, maxy: 16980661, -1180729

gives a maxResolution (whole number) of 8842.

Now, you can use 8842 in both the TileCache.cfg and OpenLayers Javascript.
A. Google BaseLayer + Road WMS Overlay = Validation approach before we proceed to TC.

1. OpenLayers (OL) Code: http://www.gisnotes.com/platform/docs/examples/GoogleWMSRoads.cfm

2. Map File Configuration: /home/map/beijing/new/beijing_google_roads

Well the above files are not exactly for TC, but it is a good demonstration that we could overlay our custom layers (WMS) on top of Google as the base layer. For a more detailed explanation regarding Google + OL, please read my previous gisnote. Also, this is a good test to see if our Mapserver mapfile configuration is correct. I do suggest not to proceed with OL + TC not unless you have validated the mapfile through OL (Google + WMS).

B. Google900913 Tilecache as baselayer

Ok.. so here it is..

1. OpenLayers Code: http://www.gisnotes.com/platform/docs/examples/TilecacheGoogle900913Base.cfm

        window.onload = function() {
            var options = {
                        projection: new OpenLayers.Projection("EPSG:900913"),
                        units: "m",
 
                        //maxResolution: 156543.0339,
                        resolutions : [156543.03390000001, 78271.516950000005, 39135.758475000002, 19567.879237500001, 9783.9396187500006, 4891.9698093750003, 2445.9849046875001, 1222.9924523437501, 611.49622617187504, 305.74811308593752, 152.87405654296876, 76.43702827148438, 38.21851413574219, 19.109257067871095, 9.5546285339355475, 4.7773142669677737, 2.3886571334838869, 1.1943285667419434, 0.59716428337097172, 0.29858214168548586],
                        //zoom: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19] @ numZoomLevels: 20
                        numZoomLevels: 20,
                        //maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 5021301.26141)
                        //maxExtent: new OpenLayers.Bounds(12823075, 4800551, 13101918, 5021301)
                        //maxExtent: new OpenLayers.Bounds(12848138, 4785083, 13080212, 5021118.5)
                        maxExtent: new OpenLayers.Bounds(-20037508, -20037508,20037508, 20037508.34)
                    };
 
            OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
            OpenLayers.Util.onImageLoadErrorColor = "transparent";
 
            map = new OpenLayers.Map('mapdiv',options);
 
            var serverURL = "/tilecache/tilecache.py";
            // start custom layer here
            var layer_obj = new OpenLayers.Layer.WMS(
                "Beijing",
                serverURL,
                {
                    layers: 'beijing_900913',
                    map: '/home/map/beijing/new/beijing_900913/beijing.map',
                    format: 'image/jpg',
                    'transparent': 'off'
                }
            );
            layer_obj.setIsBaseLayer(true);
            layer_obj.setVisibility(true);
            map.addLayer(layer_obj);

2. TileCache Configuration: /wwwroot/tilecache/tilecache.cfg

[beijing_900913]
type=WMSLayer
url=http://127.0.0.1/cgi-bin/mapserv?map=/home/map/beijing/new/beijing_900913/beijing.map
layers=beijing_900913
metatile=true
extension=jpg
levels=20
resolutions=156543.03390000001, 78271.516950000005, 39135.758475000002, 19567.879237500001, 9783.9396187500006, 4891.9698093750003, 2445.9849046875001, 1222.9924523437501, 611.49622617187504, 305.74811308593752, 152.87405654296876, 76.43702827148438, 38.21851413574219, 19.109257067871095, 9.5546285339355475, 4.7773142669677737, 2.3886571334838869, 1.1943285667419434, 0.59716428337097172, 0.29858214168548586
srs=EPSG:900913
bbox=-20037508, -20037508, 20037508, 20037508.34
#maxResolution=156543.0339
extent_type=loose
debug=on

You can either set resolutions or maxResolutions. I always wanted to be explicit, so setting the resolutions is my preference.

3. MapFile Configuration: /home/map/beijing/new/beijing_900913/beijing.map
I have a long mapfile, and using includes helped a lot, see my previous gisnote. For debugging your mapfile, read this post.

Always Remember…I believe when they made TC, I presume they always tested on WGS84(lonlat), this means if you don’t set anything explicit, it would implicitly set settings in WGS84(lon/lat)…

Ensure that you have the vector data in the necessary projection, in my case it’s 900913.

Ensure that the resolutions from OL (B.1) is reflected in TC configuration (B.2).

Ensure that the maxextents from OL (B.1) is reflected in TC configuration (B.2) as bbox.

C. Still can’t get it running?

1. Narrow down the error.

2. tail -f /var/log/apache2/error.log and access.log is your bestfriend. It’s a good starting point to trace down what went wrong. If you can’t see it from Apache’s error.log then ensure that python debugging is turned on.

3. Sometimes TC [a] gives you an obvious error or [b] its just a link to the mapserv request.

Examples of [a]:

Classic Resolution problem stated above. - If you followed my final notes above, then this should not happen. If you’ve set up things correctly but it’s still broken and you want to pull your hair out, then do a clean test stated below in D.
Cannot set image type – Check the extensions from the mapfile and TC config. Are they both in jpg’s?

The latter [b] is harder to debug. Most likely its a mapserver mapfile mishap and the easiest way to hunt this down is only thru your error.log (note: you need mapserver to have a debug=true when you compiled it, that’s another story.)

D. Doing a clean test as always
1. Always disable any caching when testing. Disable cache from your browser, for FF I use the webdeveloper toolbar. It’s as easy as Disable -> Disable Cache.

2. Stop/Start Apache. Hoping Python get’s a clean start as well. If you found any pyc (python compiled) under TC source directory… then stop Apache; remove the pycs; start Apache.

3. Seeing the same images? Always remove the image caches! rm -Rf /data/tilecache/beijing_900913

ExtJS and OpenLayers

rupert — Tue, 19 Feb 2008 00:45:18 +0000

It seems that ExtJS and OpenLayers does not blend well together. One of the bug biters that hit me was the way ExtJS was handling arrays. It would be wise for OpenLayers to be agnostic of these frameworks.

for( var i in blocks ) should be transformed to for( var i = 0; i &lt; blocks.length; i++)

I believe OpenLayers Ticket#1362 closely resembles this bug. Thanks to pgiraud for pointing me to the right direction.

Reviving an old web map with Google Maps via OpenLayers

rupert — Tue, 22 Jan 2008 01:10:09 +0000

An old coworker and I worked on a travel portal for the Philippines called travelsite.ph about 4 years ago. We are now given a task of reviving the old web application and even adding mapping functionalities. Back then, the application was using ColdFusion 4.5 and MySQL 3.

Fingers crossed we dropped the app in a ColdFusion 6/7/8 environment with no changes at all. The app still works! Awesome.. how CF really progressed through the years with backward compatibility. The only changes we made was removing the registration/sign up for a quick demo. I just laughed at the oddities and the no brainer features (pertaining to security) that I made when I was starting out.

The database was also intact and have UTM coordinates. We dropped it to a Debian mysql 5 and works flawlessly since its MyISAM. I had the coordinates exported to lon/lat, so I could directly inject it to OpenLayers/Google. After two hours of fiddling around, I got mapping embedded.. hehe.. courtesy of OpenLayers ofcourse.

Here’s a quick reminder to myself…

A. Google WGS 84 Example.

	window.onload = function() {
		var options = {
					projection: "EPSG:4326",
					numZoomLevels: 19,
					maxExtent: new OpenLayers.Bounds(120.8774, 14.3684, 121.1628, 14.7931)
 
				};
 
		// avoid pink tiles
		OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
		OpenLayers.Util.onImageLoadErrorColor = "transparent";
		map = new OpenLayers.Map('mapdiv',options);
		sat_wms = new OpenLayers.Layer.Google(
					"Layer",
					{type: G_SATELLITE_MAP}
		);
 
		map.addLayer(sat_wms);
 
		map.addControl(new OpenLayers.Control.MousePosition();
		map.addControl(new OpenLayers.Control.LayerSwitcher());
		map.addControl(new OpenLayers.Control.Scale());
 
		var center = new OpenLayers.LonLat(121.06504,14.65495);
		map.setCenter(center, 16);
	}

B. Google Mercator Projection

		window.onload = function() {
			var options = {
						projection: "EPSG:900913",
						units: "m",
						maxResolution: 156543.0339,
						numZoomLevels: 19,
						maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 5021301.26141)
					};
 
			// avoid pink tiles
			OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
			OpenLayers.Util.onImageLoadErrorColor = "transparent";
			map = new OpenLayers.Map('mapdiv',options);
			sat_wms = new OpenLayers.Layer.Google(
						"Layer",
						{type: G_SATELLITE_MAP,'sphericalMercator': true}
			);
			map.addLayer(sat_wms);
 
			// start custom layer here
			var layer_obj = new OpenLayers.Layer.WMS(
				"Beijing",
				"http://127.0.0.1/cgi-bin/mapserv",
				{
					layers: 'beijing_all',
					map: '/home/map/beijing/new/beijing_google.map',
					format: 'AGG',
					'transparent': 'true'
				}
			);
			layer_obj.setIsBaseLayer(false);
			layer_obj.setVisibility(true);	
 
			map.addLayer(layer_obj);
 
			map.addControl(new OpenLayers.Control.MousePosition());
			map.addControl(new OpenLayers.Control.LayerSwitcher());
			map.addControl(new OpenLayers.Control.Scale());
			var center = new OpenLayers.LonLat(12956625.68367, 4852316.90682);
			map.setCenter(center, 18);
		}

What’s the difference between both snippets? Obviously projection is one. Since most of my point data is in lon/lat, then the WGS84 example is good if I don’t want to overlay custom precise data. Remember the x shift problem in Google with Openlayers. The Google Mercator example is used when I want to overlay more custom data, particularly polygons/line that needs to fit on Google Layers. For more details, please see my previous blog post.

OpenLayers + Google Spherical Mercator Example

rupert — Sat, 22 Dec 2007 11:42:18 +0000

I’ve been a dormant user of OpenLayers for months (4 months?) now and it was a surprise that the svn trunk had huge differences from what I remember OL (2.4/5?) to be. One of the cool features that and the OpenLayers community contributed was the Google Speherical Mercator hack. Below is a quick step tutorial on how I was able to overlay a custom WMS to Google (set as the baselayer). For this tutorial, I want to overlay a road layer on top of Google.

1. We need to convert our data to Google Projection (Spatial Reference System: 900913). This applies to whatever kind of data (mine is vector stored both in Mapinfo and PostGis) we have. For PostGis, we need to:

INSERT INTO spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) VALUES ( 900913, 
 
'spatialreference.org', 900913, '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 
 
+x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs', 'PROJCS
 
["unnamed",GEOGCS["unnamed ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,0]],PRIMEM
 
["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Mercator_2SP"],PARAMETER
 
["standard_parallel_1",0],PARAMETER["central_meridian",0],PARAMETER
 
["false_easting",0],PARAMETER["false_northing",0],UNIT["Meter",1],EXTENSION
 
["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 
 
+units=m +nadgrids=@null +wktext  +no_defs"]]');
 
SELECT AddGeometryColumn('public','roads','the_geom_google',900913,'LINESTRING',2); 
 
UPDATE roads SET the_geom_google = Transform(the_geom, 900913);

2. MapFile Settings courtesy of SpatialReference: Google Projection

WEB
    #Other Web Config Settings goes here...
    "wms_srs"              "EPSG:900913"
END
 
PROJECTION
    "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"
END

3. By ensuring that Mapserver has the new 900913 projection, problems such as “msWMSLoadGetMapParams(): WMS server error. Invalid SRS given : SRS must be valid for all requested layers.” or “msProcessProjection(): Projection library error. no options found in ‘init’ file” will be avoided.

cd /ms4w/proj/nad/
gvim epsg
# GCS Voirol 1875 Degree
<104304> +proj=longlat +a=6378249.2 +b=6356514.999904194  no_defs <>
# GCS Voirol Unifie 1960 Degree
<104305> +proj=longlat +ellps=clrk80  no_defs <>
# Google Spherical Mercator
. . .
<900913> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs

4. Below is an example WMS Request. Note: “SRS=EPSG 900913″ is added; TRANSPARENT=true not TRANSPARENT=on; Check your BBOX settings for the correct extent.

http://127.0.0.1/cgi-bin/mapserv?
LAYERS=beijing_all
&MAP=%2Fhome%2Fmap%2Fbeijing%2Fnew%2Fbeijing_google.map
&FORMAT=AGG
&TRANSPARENT=true
&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap
&STYLES=
&EXCEPTIONS=application%2Fvnd.ogc.se_inimage
&SRS=EPSG%3A900913
&BBOX=12956687.788758555,4852222.554861524,12956993.536871642,4852528.30297461
&WIDTH=256&HEIGHT=256

5. Requesting the WMS from OpenLayers.

	var options = {
			projection: "EPSG:900913",
			units: "m",
			//maxResolution: 156543.0339,
			numZoomLevels: 18,
			maxExtent: new OpenLayers.Bounds(12823075.86334, 4800551.12375, 13101918.14248, 021301.26141)
	};
 
	// avoid pink tiles
	OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;
	OpenLayers.Util.onImageLoadErrorColor = "transparent";
	map = new OpenLayers.Map('mapdiv',options);
	sat_wms = new OpenLayers.Layer.Google(
				"Layer",
				{type: G_SATELLITE_MAP,'sphericalMercator': true}
	);
	map.addLayer(sat_wms);
 
	// start custom layer here
	var layer_obj = new OpenLayers.Layer.WMS(
		"Beijing",
		"http://127.0.0.1/cgi-bin/mapserv",
		{
			layers: 'beijing_all',
			map: '/home/map/beijing/new/beijing_google.map',
			format: 'AGG',
			'transparent': 'true'
		}
	);
	layer_obj.setIsBaseLayer(false);
	layer_obj.setVisibility(true);	
 
        map.addLayer(layer_obj);
	map.addControl(new OpenLayers.Control.MousePosition());
	map.addControl(new OpenLayers.Control.LayerSwitcher());
	map.addControl(new OpenLayers.Control.Scale());
 
	var center = new OpenLayers.LonLat(12956625.68367, 4852316.90682);
	map.setCenter(center, 17);

Transparent Overlays in TileCache

rupert — Fri, 30 Mar 2007 17:21:53 +0000

From the tilecache mailing list….

Hi Everyone,

Really appreciate all the replies…

1. Installed Imaging-1.1.6.tar.gz (PIL).

[root@rupert-linux ~]# python
Python 2.3.4 (#1, Mar 10 2006, 06:12:09) [GCC 3.4.5 20051201 (Red Hat 3.4.5-2)] on linux2 Type "help", "copyright", "credits" or "license" for more information.
&gt;&gt;&gt; import sys
&gt;&gt;&gt; print sys.path
['', '/usr/lib/python23.zip', '/usr/lib/python2.3', '/usr/lib/python2.3/plat-linux2', '/usr/lib/python2.3/lib-tk', '/usr/lib/python2.3/lib-dynload', '/usr/lib/python2.3/site-packages',
'/usr/lib/python2.3/site-packages/PIL',
'/usr/lib/python2.3/site-packages/gtk-2.0']
&gt;&gt;&gt;

2. Modified test1.cfm

     41         var options = {
     42                         controls: [new OpenLayers.Control.MouseDefaults()]
     43                       };
     44
     45         map = new OpenLayers.Map( $('map'), options);
     46
     47         var layer_base = new OpenLayers.Layer.WMS(
     48                     "Base Layer",
     49                     "#request.mapserv_tile#",
     50                     {
     51                         map: '/home/map/beijing/new/wms.map',
     52                         layers: '#request.basemap_tile#',
     53                         format: 'image/png', 'transparent': 'false'
     54                     }
     55                     );
     56
     57         var layer_road = new OpenLayers.Layer.WMS(
     58                     "Road Layer",
     59                     "#request.mapserv_tile#",
     60                     {
     61                         map: '/home/map/beijing/new/wms.map',
     62                         layers: '#request.roads_tile#',
     63                         format: 'image/png', 'transparent': 'true'
     64                     },
     65                     {
     66                         reproject: false
     67                     }
     68                     );
     69
     70         map.addLayer(layer_base);
     71         layer_base.setIsBaseLayer(true);
     72
     73         layer_road.setIsBaseLayer(false);
     74         map.addLayer(layer_road);

3. tilecache.cfg. Commented metaTile=true http://222.128.19.19/tilecache/tilecache.cfg

     47 [basemap]
     48 type=WMSLayer
     49 url=http://127.0.0.1/cgi-bin/mapserv?map=/home/map/beijing/new/wms.map
     50 layers=district,greens,major_river,minor_river
     51 #bbox=-180,-90,180,90
     52 #metaTile=true
     53 extension=png
     54
     55 [roads]
     56 type=WMSLayer
     57 url=http://127.0.0.1/cgi-bin/mapserv?map=/home/map/beijing/new/wms.map
     58 #layers=road4,road4label,road3,road3label,road2,road2label,road1,road1label,road11,road11label
     59 #bbox=116.1737,39.8211,116.5640,40.0799
     60 #maxresolution=1.40625
     61 #bbox=-180,-90,180,90
     62 layers=road1,road1label,road11,road11label
     63 extension=png
     64 #metaTile=true

4. Modified wms.map http://222.128.19.19/tilecache/wms.map

OUTPUTFORMAT
     NAME png
     DRIVER "GD/PNG"
     MIMETYPE "image/png"
     IMAGEMODE RGB
     EXTENSION "png"
     FORMATOPTION "INTERLACE=OFF"
END

5. Checked access_log. “transparent=true” exists…
192.168.1.150 - - [30/Mar/2007:13:46:26 +0800] "GET /tilecache/tilecache.py?MAP=%2Fhome%2Fmap%2Fbeijing%2Fnew%2Fwms.map&LAYERS=r oads&FORMAT=image%2Fpng&TRANSPARENT=true&SERVICE=WMS&VERSION=1.1.1&REQUEST=G etMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A4326&BB OX=116.334229%2C39.891357% 2C116.345215%2C39.902344&WIDTH=256&HEIGHT=256 HTTP/1.1" 200 14580

Now, this is really weird. I have “transparent”: true in test1.cfm all the time. That didn’t worked.

For every test iteration i made, I always tried clearing the cache, removing the python compiled scripts, then restarting Apache just to get a clean state..

rm -Rf /usr/local/apache2/htdocs/tmp/* rm /wwwroot/tilecache/TileCache/*.pyc /etc/init.d/httpd restart

Then I tried appending “transparent=true” to tilecache.cfg based on Eric’s suggestion…
That worked. Now I wonder why… Nevertheless, its working now. Again many thanks to everyone…

Rupert

On Fri, Mar 30, 2007 at 01:57:43PM +0800, Rupert de Guzman Jr wrote:
> Hi Everyone,
>
> Really appreciate all the replies…
> Then I tried appending “transparent=true” to tilecache.cfg based on
> Eric’s suggestion…
> That worked. Now I wonder why… Nevertheless, its working now. Again
> many thanks to everyone…

TileCache pays almost no attention to the URL: Only the BBOX and the layername matter. Anything else is simply ignored: so your transparency being set in OpenLayers actually has 0 affect.

The reason for this is that TileCache can only store one copy of an image. If the URL parameters modified the content, you could get an inconsistent cache.

This is ‘by design’, insofar as there is no obvious solution (other than to complain more loudly when TC Gets parameters it isn’t expecting, which is an outstanding FIXME in the code). The lack of error message is not by design, and I’m sorry you got bit by the poorly documented behavior.

Regards,
–
Christopher Schmidt
MetaCarta

OpenLayers and Google Layer Zoom fix

rupert — Tue, 20 Feb 2007 11:32:18 +0000

I have finally fixed the disappearing layer on the layer switch when we try to overlay the layer on top of Google. I edited Google.js to reflect the ff:

 
    MAX_ZOOM_LEVEL: 22,
 
    /** Hardcode these resolutions so that they are more closely
     *   tied with the standard wms projection
     *
     * @final @type Array(float) */
/*    RESOLUTIONS: [1.40625,0.703125,0.3515625,0.17578125,0.087890625,0.0439453125,0.02197265625,0.010986328125,0.0054931640625,0.00274658203125,0.001373291015625,0.0006866455078125,0.00034332275390625,0.000171661376953125,0.0000858306884765625,0.00004291534423828125],*/
 
RESOLUTIONS:[1.40625,0.703125,0.3515625,0.17578125,0.087890625,0.0439453125,0.02197265625,0.010986328125,0.0054931640625,0.00274658203125,0.001373291015625,0.0006866455078125,0.00034332275390625,0.000171661376953125,0.0000858306884765625,0.00004291534423828125,0.0000214576721191140625,0.000107288360595703125,0.0000053644182978515625,0.000002682209014892578125,0.0000013411045074462890625,0.00000067055225372314453125],

TileCache Experiment

rupert — Fri, 16 Feb 2007 00:55:48 +0000

I am now able to do tilecache using TileCache1.3 from metacarta. Base from archives (archive-user.txt)

From crschmidt at metacarta.com  Wed Nov 22 17:54:29 2006
From: crschmidt at metacarta.com (Christopher Schmidt)
Date: Wed, 22 Nov 2006 17:54:29 -0500
Subject: [OpenLayers-Users] TileCache - Tiling issues
In-Reply-To: <4564D326.6020607@refractions.net>
References: <4564D326.6020607@refractions.net>
Message-ID: <20061122225429.GA18180@metacarta.com>

On Wed, Nov 22, 2006 at 02:45:58PM -0800, Ben Brehmer wrote:
> Hello everyone,
>
> I have setup a basic OpenLayers application with TileCache doing the
> server-side caching. I was wondering if there is a way to pre-cache all
> the tiles (besides panning/zooming everywhere on the map)? I know in
> kamap there is a script that can be run to pre-cache all the tiles. Is
> there something similair for TileCache?

In the TileCache directory, there is a 'Client.py' script. To pre-cache
your data, use it in the following manner:

python Client.py "http://example.com/tilecachelocation/tilecache.cgi?"
"layername" startzoomlevel endzoomlevel [BBOX]

Something like:

python Client.py "http://labs.metacarta.com/wms-c/Basic.py?" "basic" 0 16

Is what we used to precache all of the Vmap0 data in the MetaCarta VMap0
layer.

> Also, I have attached two jpegs. Each has part of a symbol or label
> chopped off. I believe that the "chopping" occurs at the edge of a tile.
> Has anyone ever experience something like this in OpenLayers?

This is based on your Mapserver setup, rather than something specific in
OpenLayers. Using WMS would result in the same visual result. Labels can
have this prevented using the "PARTIALS OFF" on your label layer, if
you're using Mapserver. I'm not aware of a way to prevent this in symbol
generation. 

We are currently working on ka-map style rendering to add to TileCache,
to help people not run into this issue. No timeframe available yet on
when that'll be released. 

Regards,
--
Christopher Schmidt
MetaCarta

1. TileCache Configuration: tilecache.cfg

[cache]
type=DiskCache
base=E:\\usr\\local\\apache2\\htdocs\\tmp\\
 
[basemap]
type=WMSLayer
url=http://127.0.0.1/cgi-bin/mapserv.exe?map=/home/basemap/wmstest_longlat.map
layers=district,greens,major_river,minor_river
extension=png
 
[roads]
type=WMSLayer
url=http://127.0.0.1/cgi-bin/mapserv.exe?map=/home/basemap/wmstest_longlat.map
layers=road4,road4label,road3,road3label,road2,road2label,road1,road1label,road11,road11label
extension=png

2. Calling CFM Script: Test.cfm

    <cfset request.mapserv="http://127.0.0.1/tilecache/tilecache.py"> 
 
    <script src="/OpenLayers-2.2/lib/OpenLayers.js">script>
    <script type="text/javascript">script>
                //var lon = 116.3842;
        //var lat = 39.9150;
        var lon = 116.3846;
        var lat = 39.9202;
        var zoom = 16;
        var map, markers;
 
        function init(){
      	    map = new OpenLayers.Map( $('map'), { maxResolution: 'auto'});
 
	    var layer_base = new OpenLayers.Layer.WMS(
					"Base Layer",
					"#request.mapserv#",
					{
						layers: 'basemap',
						format: 'png', 'transparent': 'off'
					}
					);
 
                map.addLayer(layer_base);
	   layer_base.setIsBaseLayer(true);	
 
               ...more code here...
 
       }
cfset>

I want to fine tune this script since I am getting odd tiles like duplicate tiles or tiles shown of different scale on the same scale.

3. Precaching:
/d/Python24/python.exe Client.py “http://127.0.0.1/tilecache/tilecache.py” “roads” 14 16 116.35397,39.88984,116.42988,39.91918

I need to understand the “cache hit” or “cache miss” during execution.