[OSM-dev] Projection problems
Hi all, I wonder if any one could be so kind as to help me out with a problem I am having with projections: I am trying to convert from lat/long coords to the Mercator projection as is used in osm2pgsql I am using this code: http://wiki.openstreetmap.org/index.php/Mercator#Java_Implementation The Lat/Long I am using is (bounding box around a street I know): -0.90362548828125,51.38892310050485 to -0.90087890625,51.38720911696496 However, when converted to Mercator projection as per the above Java code, I get the following: -100591.12922329194,6656970.686752424 to -100285.38111015123,6656665.738991335 The y values (6656970 - 6656665) do not match up with data the postgres database: LINESTRING(-100491.52 6690303.05,-100474.32 6690280.11,-100456.16 6690259.1,-100438.02 6690235.21,-100434.02 6690222.73,-100430.37 6690211.33,-100433.23 6690176.94,-100434.19 6690146.36,-100432.48 6690134,-100430.37 6690118.64,-100417.95 6690093.81,-100398.83 6690072.78,-100373.27 6690047.38,-100370.16 6690038.6,-100327.34 6689918.14,-100309.98 6689869.27,-100245.01 6689884.55) Note - all the Y values in the DB are ~669 not ~665 as returned by the mercY() function. The effect of this is that an SQL query to pull data from the database is not fetching the correct data. Would there happen to be an expert on this list that help out with the accuracy of the projection code at the above link? It only affects the Y coordinate, X seems fine. Many thanks in advance. -- Brad. ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Projection problems
Many thanks for your answers. I will have a look through the osm2pgsql code to try figure out the scaling factor. -- Brad On 16 Dec 2008, 5:27 PM, Thomas Wood grand.edgemas...@gmail.com wrote: osm2pgsql uses a spherical mercator projection which cuts down on the amount of math required to produce a reasonable estimation of the earth for our uses. It's not a 'proper' projection in the GIS sense, but it works for our purposes. http://wiki.openstreetmap.org/index.php/Mercator#Spherical_Mercator I'm not sure what scaling factor osm2pgsql uses Somewhat related implementations are at http://wiki.openstreetmap.org/wiki/Tilenames#Java 2008/12/16 Bradley Kite bradley.k...@gmail.com: Hi all, I wonder if any one could be so kind as to help me out with a problem I am having wi... ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev -- Regards, Thomas Wood (Edgemaster) ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
[OSM-dev] Correct place to submit patches?
Hi all, I'm new to this mailing list and to OSM in general so would like to introduce myself first. I am Bradley Kite, and have an interest in getting Mapnik/OSM running on the Android mobile platform: http://code.google.com/p/osmdroid/ Currently, the software downloads map tiles on demand (and caches them locally), but I have been working on having a map-tile renderer work on the phone itself, from a database on the phone's SD card (so that map-tiles can be provided in the absence of phone signal). To this aim, I have mostly ported mapnik to Java (its not complete yet, but not far from it) (http://code.google.com/p/osmdroid/source/browse/#svn/branches/osm-contributor) and have patched osm2pgsql so that it can output to an sqlite database instead of postgres (sqlite libraries etc. come with the phone's software stack). I'd like to submit this patch back so that it could be included in future versions of osm2pgqsl - so that others can build sqlite databases of their local countries that can work on the phone. Please advise on the correct procedure. Regards -- Brad. ___ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
