I have been seeing new Bing imagery show up in Michigan in areas I edit. Although updated imagery is welcome, I would say my subjective view of its quality makes it a mixed situation. Subjectively I would describe it as more blurry or less distinct. Maybe the new imagery has lower contrast.

The problem I see most is with creating new or recreating existing imagery offsets in JOSM. I have created and uploaded many by using survey marks or benchmarks with known coordinates. An example that is no longer visible is at N 42 55 06.65005 W 084 32 34.97447. Contrast that with the Mapbox or Ersi World imagery where the concrete circular base is visible along with witness post just to the west.

I have started to add offsets for Ersi World which seems to have more distinct imagery. For the few offsets that I had added I have been quite pleased to see how close Ersi World was to begin with. Most have been within a meter accuracy.

In a previous diary entry I documented my use of survey points for creating imagery offsets for Bing and USGS Large Scale Imagery. At the time I did not think to create them for USGS Topographic as the points were not on the map. However, I came to realize I can still improve the offset there if features (primarily roads) in the area survey point are in good alignment and can be seen on that layer. These are not as good as the satellite but it would at least be an improvement for tracing old roads, trails and wetland contours.

I also decided I should create offsets for Mapbox Satelitte. I do not use that layer as much as the resolution or clarity seems a little less. In addition, I sometimes have issues with cloud cover on that layer. Creating the offset does not take that much more effort and it might be of use sometime for myself or someone else. The cloud cover issue means I was not able to create an offset each time.

Entry updated to move personal documentation to personal wiki.

I thought I would record what I do for traces for any future reference. This applies to walking or driving traces.

For hardware I use a Holux M-1000C Wireless GPS Logger. This is an external bluetooth GPS receiver I use with my phone. Prior to June 2013, the phone I used was a Samsung Galaxy S. After that date I have used a Samsung Galaxy S3.

The GPS on my original phone was particularly bad. I believe when the Galaxy S was originally released the GPS was basically broken. I was primarily using the GPS in my phone for geocaching so the poor accuracy of the GPS was frustrating. I also drained the battery quite quick between the GPS and downloading maps. Improving accuracy and battery life were the main reasons for getting a separate receiver.

For software I use Locus Map Pro. Locus Map has good geocaching capability as part of its significant mapping capability features. The reason I was looking at a mapping application for geocaching was that I was looking for good off-line map capability. Locus Map can store tiles for off-line use or use off-line .map files rendered by the Mapsforge library. I have a limited dataplan so all the maps being downloaded for geocaching were using up all my data.

I started mapping on OpenStreetMap to improve areas I wanted to do geocaching in; for example, parks. There are phone applications focused on collecting OSM data. However, the ones I have tried all use on-line maps so that is not desirable for me. So I continue to use Locus Map to record waypoints of amenities or features I wish to map. I create my own off-line maps using a Mapwriter plugin custom tagging file with Osmosis to create the file and a custom Mapsforge theme to render the map. That way I see everything I add on my phone.

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I came to the conclusion recently that I needed to start understanding and being concerned about imagery offset. This started when Bing imagery changed and I began to notice that buildings had shifted. I also began to use other imagery such as USGS Large Scale Imagery, which also did not necessarily align with Bing imagery.

Having decided to learn about imagery offset and use it I came to discover there had been no offsets created in the areas I typically mapped. Now I needed to understand how to create offsets.

I had read discussions of using GPS traces to establish an offset based on roads. In looking at the traces that were being downloaded within JOSM those traces seemed less than ideal. This was due to randomness of lanes driven in, possibly poor sampling resolution, as well as possibly poor GPS accuracy or bounce. It was going to take a larger sample to reduce that. So I started recording and uploading traces myself.

The slowness of creating a decent sample caused me to think about how to do this quicker. I considered finding a fixed and visible feature and doing some longer GPS averages on those sites over a number of days. It then occurred to me I should just find some benchmarks or survey marks as the National Geodetic Survey (NGS) already provides the coordinates for those.

I was familiar with benchmarks from the geocaching I do. It is a subtype of geocaching, at least in the U.S. In doing a little more searching on offsets I found this was a suggested approach so I proceeded on with it. I thought I would document and share my techniques to the extent they may help someone else or could be improved by someone else’s suggestions.

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I made my first contributions to HOT yesterday. It took me longer to find a project felt I could make good or confident updates to as it did to make the updates. Some of the Africa projects seemed a bit daunting to start with in trying. The updates I made were to #836 - Missing Maps: Displaced communities, Iraq (east).

Although I could reasonably see the roads, I was still challenged in how to classify them. I started with what I thought was a primary and then proceeded down from there. I found inconsistent classification elsewhere in the project so that was not a guidance. I did think that at least some of the roads I classified were too high, for example, the secondary probably should have been tertiary and the tertiary should have been a mix of unclassified or track.

I did find some United Nations Assistance Mission maps housed on the European Country of Origin Information Network site. There were enough different maps for me to confirm that the primary road I had identified would best be still considered that way. However, the rest of the roads I added should probably be demoted, as I was wondering.

Whether these maps are permissible to trace, I will still need to find out. [Update: assume no] I am not sure there is any road tracing value to these. However, some could provide value in terms of waterways. I see a lot of dry stream and river beds on the satellite images. I cannot tell if any water ever flows in them.

08.2002 - UN Assistance Mission for Iraq: Map of the Kalar district

22.07.2003 - UN Assistance Mission for Iraq: Map of the Sulaymaniyah Governorate

[2003 - UN Assistance Mission for Iraq: Road map of the Diyala governorate] (http://www.ecoi.net/file_upload/1222_1190358975_diyala-governorate-road-map.pdf)

2003 - UN Assistance Mission for Iraq: Road map of the north Diyala governorate

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