I want to do a few tiny mapping projects in Maine, because I have some local knowledge, and I know people there who need maps. But I’ve run into a number of issues, and it has been suggested that I should write these up for a larger audience.

County borders

The county borders in Maine are wildly inaccurate, at least along the coast. They’re based on a low-res trace of the shoreline, which has several problems:

1. You get a lot of cluttered borders deep within a county.
2. The borders swerve randomly all over coastal islands. This is ugly, and incorrect.
3. Many smaller islands are omitted entirely.

Here’s a sample. Every piece of land on this map actually falls within the county line, and I’d imagine that the ocean is under county jurisdiction as well:

Now, we actually have pretty accurate county data in various GNIS and TIGER fields, if we know how to interpret it. Let’s set up a JSOM filter to exclude everything but Lincoln county data and the border line:

… Zobrazit celý záznam

I went for a lovely afternoon hike today, and added a partial set of hiking trails through some nice woods. These are marked highway=footway. You should be able to see these at the map location associated with this diary entry.

Any suggestions on how I might improve this? I'm still a novice, and I'd like to make sure I'm doing everything correctly before adding more trails.

I added by first street numbers today, up along Route 5 and some of the surrounding streets. I think I'm getting the hang of it: addr:housenumber and addr:street are pretty easy.

I've decided that GNIS landmarks are highly suspicious: I've found town halls on the wrong side of the river, churches erroneously placed in the deep woods, and multiple stacked landmarks. So far, they've been pretty much entirely wrong.

On an unrelated note, I despair about ever getting an accurate amenity map in the US through manual editing, even with OSM Tracker and similar tools. Better, perhaps, to get street numbers at every intersection, crawl the web for addresses, and geocode them.

I wonder if the Google Street View cars are running OCR on images of business signs? I can't imagine that they're not—it seems entirely obvious after two days of mapping.

I spent today walking around with a Nexus One and OSM Tracker for Android. It reported 2m accuracy in the open, and about 3 or 4m near buildings, which is quite good compared to my old Garmin GPS. I added many new amenities to White River Junction, plus a footpath and park.

Feeling more ambitious, I made a fairly major update to a hill and intersection on Route 5 that has seen massive construction work over the last few years. With any luck, OSM-based navigation software should now be able to substantially outperform Google Maps near this intersection, because it will know about the new roads and turn restrictions.

I relied on GPS tracks taken from the sidewalks on either side of the road, so there might be some occasional position and shape errors on the order of 5 to 10 feet.