Re: [OpenMap Users] Newbie questions....

From: Don Dietrick <>
Date: Fri, 28 Jul 2006 09:21:41 -0400

On Jul 27, 2006, at 4:35 PM, JR Andreassen wrote:

> Thanks for getting back to me.
>>> Issues so far:
>>> How to you specify the base map ?
>> You would configure a layer to display the data you want. For
>> the default OpenMap application, the layers are specified and
>> configured in the file. That file has
>> instructions for modifying itself.
>>> I can't find any reference on where to change the base map Image.
>>> (Or is there a way to specify a Shape/other as the background)
>>> Does it /How do I handle Quadrangle/TIFF images ?
>> The easiest way to display images is to use the
>> CSVTiledImagePlugIn. The JavaDocs for the CSVTiledImagePlugIn
>> describe how to create a CSV file that list the images and their
>> locations, and the plugin can be added as a layer to the
>> application (via the file), with that csv file
>> noted in the properties for that plugin.
>> I'm not sure if TIFFs are handled by the general JRE, come to
>> think of it. You might have to install the JAI package (Java
>> Advanced Imaging) to get TIFF functionality.
> I can handle that...
>>> Does it /How do I handle Segmented data and transitions?
>>> We have several datasets that we'll be based on
>>> (
>>> geospatial_main.asp)
>>> These data sets(roads, etc) are split into areas(counties) since
>>> they are rather large.
>> Shape files can be read to create OMGraphics, which are the
>> objects rendered to the map. They know how to position and
>> render themselves. There are Layers that create OMGraphics out
>> of Shape files, and one (MultiShapeLayer) that handles more than
>> one Shape file. If you are going to have a lot of data...
>>> Does it /How do I handle monster datasets ?
>> you should load the data sets into a database (MySQL, PostGRES
>> with PostGIS, Oracle) and use a layer to retrieve the geometries
>> from the database based on the projection.
> Newbie question: Is the projection your subset of the world vs
> "zoom-factor" ?

The projection is a description of the map window - there's a
projection type associated with the object, a center point of the
projection at the center of the window, a scale, and pixel height/width.

Projection's forward() methods translate lat/lons to pixel
coordinates, and inverse() methods translate pixel coordinates to lat/
lon coordinates.

The MapBean (the main map window object) controls the Projection
object and lets its layers know when it has changed.

> Can you make a projection that is relative to the "current
> possition" with no refresh until you reach a certain offset from
> the edge ?

You can change the projection on the MapBean whenever you like. The
layers are reactionary to the MapBean's notifications. If a layer
needs to change the projection, it has to tell the MapBean.

>> A MySQL layer is part of the distribution, and an
>> OracleSpatialLayer was posted to the mailing list and is
>> available in the archives.
> The DB approach is appealing to us, since we have a DBM(DB/2) on
> each machine. The problem with the DB/2 GeoSpatial extender is that
> it's $9k per machine.
> Given that we have over 2K users that's way outside our budget. So,
> is there a X./Open standard for GeoSpatial data ?
> I might be able contribute some in that area.....

The Open GIS Consortium (OGC) has a standard for storing data in a
database, Simple Features for SQL.

I don't know if there is an open source DB2 geospatial extender, or
if you want to add one of the other free databases to your machines
to handle large amounts of spatial data.

- Don

>> Does it /How do I handle Lat/Lon to Layer serches ?
>> If you are using a database with large datasets, it's probably
>> better to do the search on the database. You can also work with
>> the OMGraphics to do spatial searches for those objects rendered
>> on the map.
>> There's a developer's guide available at:
> Got that one...
>> Hope this helps,
> It does indeed...
> Thanks
> JR
> JR Andreassen
> Strategic Database Inc.
> --
> [To unsubscribe to this list send an email to ""
> with the following text in the BODY of the message "unsubscribe
> openmap-users"]

Don Dietrick,
BBN Technologies, Cambridge, MA

[To unsubscribe to this list send an email to ""
with the following text in the BODY of the message "unsubscribe openmap-users"]
Received on Fri Jul 28 2006 - 09:23:02 EDT

This archive was generated by hypermail 2.3.0 : Tue Mar 28 2017 - 23:25:07 EDT