Eastern Bulacan, Pampanga and Nueva Ecija imagery update in Openstreetmap

We have new imagery available for tracing in OSM along the eastern section of Bulacan, Pampanga and Nueva Ecija.

Last year, we have imported Quickbird imagery in Pangasinan. This time, SPOT Asia through a local distributor (Certeza Infosys) extended assistance to provide us with SPOT5 10 meter color imagery . Unlike the previous Quickbird imagery import, I felt the SPOT5 image needs a some remote sensing massage to be more useful for OSM’s purpose. The raw color images have several limitations:

• Large portions of the east of the image is covered with clouds, a total waste of disk space to load for OSM’s web-based imagery overlays.

• Image is too dark which makes it difficult to identify and discriminate features.

• Default image rectification is off by ~10-50 meters.

Processing procedures
I have outlined the processing procedures below.

Color balancing
I performed color balancing using the i.landsat.rgb module of GRASS GIS. This was designed for auto-balancing LANDSAT color channels but is useful for other imagery as well. I then assigned NULL values to all pixels with 0 digital number using r.null in GRASS GIS.

You can perform a similar approach using any image manipulation application (like GIMP). I simply used GRASS GIS because it can easily process such large imagery even with my meager hardware.

The output image shows a much better results.

Image Registration/Rectification
Rectification converts the imags to a standard map coordinate system. (http://en.wikipedia.org/wiki/Image_rectification). To put it in simple terms, this process ties the image pixel to a specific location on the Earth’s surface. It requires the identification Ground Control Points (GCPs) as reference to calculate the necessary image transformation.

The SPOT5 image covers a very large area (60 km by 60 km). It can take me months to collect GCP in order to rectify the image. Adhering to the principles of “crowdsourcing”, I initially thought of using the excellent web-based MapWarper service. I can just upload the map and allow others to add GCPs based on OSM maptiles. However, this comes with several limitations:

• A single image for MapWarper should be at maximum of 5 MB and 1500 x 1500 pixel resolution. Not enough for my 3 GB, 30000 x 30000 pixel image!

• The identification of GCPs is dependent on the available data contributed in OSM. This becomes problematic when data is sparse and you can’t easily identify the accuracy of the sources.

My only recourse is to rectify the image myself. However, collecting GCPs across the whole image can be a daunting task.

I realized another option is to get all GPS traces uploaded in OSM within the area and select good traces to align and rectify the image. I found several good ones with multiple traces of the same road. The multiple traces is good in approximating the position of GCPs.

After a few hours of GCP hunting and adjustments in QGIS and the Georeferencer plugin, the image is now rectified and fits nicely to the GPS traces. Although there maybe some errors , I think this is good enough for OSM.

Big thanks again to Andy for creating map tiles using Mapnik’s generate_tiles.py magic.

You can now use the data in any of the OSM editors (potlatch, josm or merkaartor).  Instructions on how to use them are available in the wiki.

I’m sure there are better ways to do it, but this post highlights how you can re-purpose user contributed GPS tracks in OSM to rectify imagery (and another good reason why OSM contributors should upload GPS tracks).

Enjoy!

lost in the arc* licensing maze

Can someone help me out here.

A colleague wants some advise on developing an application based on ArcGIS stack with the following generic features:

• access and edit data on field;

• perform basic overlay analysis and attribute queries;

• monitor heavy equipment (i. e. delivery trucks) from raw material sources to the factory;

• provide cartographic output either as paper map or a web app;

For a geo-geek using mostly free and open source tools, I am at a loss in understanding ArcGIS licensing options. Terms such as “licensing by number of cores”, “single use”, “authorization process”, “license management” baffle me.

In shopping for open source options I’d always look at the functionality first, license was never an issue.

And it seems I’m not the only person having problems with it. (See comments from james’ blog)

free paper roadmap from maposmatic

Remember those EZ Roadmaps we used to buy? Now you can create a similar map based on Openstreetmap data.

MapOSMatic is a free service that:

allows you to generate maps of cities using OpenStreetMap data. A city map is made of two pages:

* The map itself, splitted in squares allowing to easily look for streets;
* An index of the streets with references to the squares on the map.

The generated maps are available in PNG, PDF and SVG formats and are ready to be printed.

As the data used to generate maps is coming from OpenStreetMap, you can freely (under the terms of OpenStreetMap license) reuse, sell, modify, … the generated maps.

I created my own map of Provident Village. I plan to use this paper map to verify and add more details particularly for Ondoy-damaged roads and structures around the neighborhood this weekend. Here is my job request, and below are the output images.

Map

Index

The data is updated daily, so when you update or add new data in Openstreetmap, you can request a new map the next day with all your updates included. Nice!

The map creation time is very fast (it took less than a minute), however, you may have to wait for a long queue line depending on the request load (mine took 17 hours, maintainers promised it should be quicker in the coming days). Nevertheless, the update is so much faster than the local publisher’s update cycle. :)

Everything is open source, so you can roll your own service if you want to. Enjoy!

osm-ph christmas micro-mapping party 2009

Everyone is invited to join the worldwide Openstreetmap Christmas Party this year. We have small event cum micro-mapping here in Metro Manila.

Details

• Date: December 12, 2009 8:00 AM till 5:00 PM
• Mapping Area: Cubao/Araneta Center
• Mapping Goal: To map amenity details around Araneta Center with walking-papers and GPS.
• Schedule:  8:00 AM - Meet at Starbucks Araneta Center (approximate location). 8:00 – 3:00 - Collect mapping data.
  3:00 – onwards – Back to Starbucks to upload data, share stories and plans for next year.

Add your name here if you want to join.

UPDATE: Eugene posted a post-party report in his blog.

OSM-PH presentation video at SOTM’08

Eugene reminded us that Andy finally uploaded the videos of Openstreetmap’s State of the Map Conference last year in Limerick.

I helped Mike create the presentation material. I think he gave a good overview of the status of mapping in the Philippines back then.

In case your curious, that’s me in the first slide :).