Hello list,
I really haven’t a clue where to start with this so any pointers would be gratefully received.
I have a global data set residing in a postgres/postgis database. The geographic spread of the data is random, some areas have a lot of points whereas others have quite sparse points. The data basically boils down to a location and an integer value between 0 and 4.
I would like to represent this data as a series of fixed sized cells (shape not important but hexagonal would look nice!). If no data point resides within a cell I’d like to colour the cell purple. If more than one data point resides within a cell I’d like to colour it based on only the highest number amongst those points within the cell.
I’d like the cells to completely cover (and probably be clipped by) by coastline data. The net effect I’m after would be the landmasses shown as a patchwork of coloured cells.
I have tried playing around with a gs:BarnesSurface but I don’t see able to get the results I’m after with this method. Any ideas?
Thanks
Chris
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BarnesSurface is not what you want - it does a lot of interpolation that doesn’t sound as if it’s required.
One way to do this is to do the aggregation on the PostGIS side. There’s various ways to do this:
- You can create a grid of cells of the desired shape and dimensions (e.g. either square or hexagonal), spatially join this to the source data points, and then aggregate by cell.
- A slicker and faster way is to compute the cell index of each point mathematically (which avoids the need for the spatial join). For squares this is fairly trivial, for hexagons it’s harder. Then do the aggregation as before. The cell geometry needs to be computed as well, but only for display purposes.
It would also be nice to have this functionality run dynamically as a GeoServer process running as a Rendering Transformation. This would be similar to the existing PointStacker process, but would aggregate to cell polygons and then return the cells as a feature collection.
On Wed, Feb 6, 2013 at 1:04 AM, Chris Haste <CHaste@anonymised.com> wrote:
Hello list,
I really haven’t a clue where to start with this so any pointers would be gratefully received.
I have a global data set residing in a postgres/postgis database. The geographic spread of the data is random, some areas have a lot of points whereas others have quite sparse points. The data basically boils down to a location and an integer value between 0 and 4.
I would like to represent this data as a series of fixed sized cells (shape not important but hexagonal would look nice!). If no data point resides within a cell I’d like to colour the cell purple. If more than one data point resides within a cell I’d like to colour it based on only the highest number amongst those points within the cell.
I’d like the cells to completely cover (and probably be clipped by) by coastline data. The net effect I’m after would be the landmasses shown as a patchwork of coloured cells.
I have tried playing around with a gs:BarnesSurface but I don’t see able to get the results I’m after with this method. Any ideas?
Thanks
Chris
*** This communication has been sent from World Fuel Services
Corporation or its subsidiaries or its affiliates for the intended recipient
only and may contain proprietary, confidential or privileged information.
If you are not the intended recipient, any review, disclosure, copying,
use, or distribution of the information included in this communication
and any attachments is strictly prohibited. If you have received this
communication in error, please notify us immediately by replying to this
communication and delete the communication, including any
attachments, from your computer. Electronic communications sent to or
from World Fuel Services Corporation or its subsidiaries or its affiliates
may be monitored for quality assurance and compliance purposes.***
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