On Mon, Oct 18, 2010 at 7:35 AM, Richard Greenwood <[email protected]> wrote: > On Sun, Oct 17, 2010 at 7:17 PM, P Kishor <[email protected]> wrote: >> I have created a control after the "OpenLayers Measure Example" >> [http://openlayers.org/dev/examples/measure.html], and all is good. >> The user can draw a poly in the browser, and measure the area. Now, I >> want to save the drawn polygon on the server-side, so I can recreate >> it later. I guess if I could convert the drawn poly to a geojson >> object, I could save it on the server. Then, at the click of a button, >> the saved map extent and the drawn feature could be recreated. Any >> ideas how I could do this? > > Puneet, > > I send the object to a PHP script on the server and save it into a > PostGIS database.
Right, but what is the call for getting the object from the OL client? I guess I should simplify my question by breaking it up into two parts -- 1. Once I have drawn a poly on the map (using the measure control), how do I get its geometry that I can then send to the server? All I need to know here is the appropriate method that will give me the geometry of the poly I drew. 2. What all are the essential params required to reconstruct the state of a map view in OL? I guess I need to know the layers that are visible, and the map extent that needs to be saved. In my use case, since I also want to reconstruct the poly that was drawn, I need that geometry. The last I can get via #1 above, but how do I get the "current" map extent and the names of the layers that are currently visible? Is there a method that can "dump" all the information required to reconstruct the current state? > I don't use GeoJSON or any standard format, but > probably should. What format do you use? > Do a POST not a GET as geometries can become quite > big. And I always do an ST_ISVALID() before inserting it. If you're > working with polygons it is not uncommon for the user to draw an > invalid poly and there is nothing to stop that poly from being > inserted. It is only when you query that invalid poly that the > problems begin. If you're only working w/ lines and points then it's > not a worry. > > Similarly, I query a PHP script for an object's extent using the > PostGIS ST_EXTENT() function, and pass that to OpenLayers. ST_EXTENT() > is an aggregate function, so you can pass a set of records and get the > bounding box of the whole set, e.g. if you had a bunch of address > points: > SELECT ST_EXTENT(wkb_geometry) WHERE zipcode='83014'; > Would return the bounding box of the whole set of matching points. > > In both cases (saving and retrieving) I'm using home grown AJAX calls > to home grown PHP scripts. I'm sure others will suggest WFS-T which > has it's strengths, but forces you into WFS. I'm doing everything with > native MapServer layers. Simple is better. I am sticking to WMS with MapServer. For geographic data I have a mix of shapefiles, images, and PostGIS. For everything else, I am using SQLite (for now). Its all working quite well. > > Regards, > Rich > > >> -- >> Puneet Kishor http://www.punkish.org >> Carbon Model http://carbonmodel.org >> Charter Member, Open Source Geospatial Foundation http://www.osgeo.org >> Science Commons Fellow, http://sciencecommons.org/about/whoweare/kishor >> Nelson Institute, UW-Madison http://www.nelson.wisc.edu >> ----------------------------------------------------------------------- >> Assertions are politics; backing up assertions with evidence is science >> ======================================================================= >> _______________________________________________ >> Users mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/openlayers-users >> > > > > -- > Richard Greenwood > [email protected] > www.greenwoodmap.com > -- Puneet Kishor http://www.punkish.org Carbon Model http://carbonmodel.org Charter Member, Open Source Geospatial Foundation http://www.osgeo.org Science Commons Fellow, http://sciencecommons.org/about/whoweare/kishor Nelson Institute, UW-Madison http://www.nelson.wisc.edu ----------------------------------------------------------------------- Assertions are politics; backing up assertions with evidence is science ======================================================================= _______________________________________________ Users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/openlayers-users
