I just finished mapping a number of GNIS records for summits in the other 49 States and US Territories. With a couple of rare exceptions, these were all records for features that were not present in OSM. I was looking at doing the same for Alaska, but the total of 1700+ records is more than the rest of the entire US and more than I’m prepared to map by hand. Instead, I’m proposing to import these records without manual review.
The method I used for the other States was to use automated conflation to find GNIS records that were not in OSM. Then I reviewed each one by hand and made corrections using aerial imagery, USGS Topo, and 3DEP. That works fine when it’s 25 nodes at a time.The vast majority of records needed either a minor adjustment of the location or no correction at all. But there were rare cases where corrections were needed, and importing the data without reviewing it would mean these corrections wouldn’t be made. In general, the corrections were:
- Tagging - GNIS classes are very broad and include things that are mapped in different ways in OSM. In the other States, I used key words in the names to identify some of the variations in tagging, then reviewed local topography to make corrections.
- Location - GNIS coordinates are frequently off by a small distance relative to USGS Topo and 3DEP. Some rare outliers are off by a substantial distance. In the other States, I checked and corrected each location against aerial imagery, USGS Topo and 3DEP.
- Name - GNIS has rare typos which can often by corrected by checking USGS Topo.
- Duplicates - GNIS occasionally has duplicate records for the same feature. These can be identified by either manual review or automated searches.
- Categorization - GNIS records are rarely miscategorized. When it does happen, it’s usually man made features being miscategorized as natural features.
For Alaska, I am proposing to import the data without the manual reviews. That would mean using key words in the names to determine tags (e.g., “Mountains” with an S implies
natural=mountain_range). And I plan to do some automated checks to remove duplicates. But I will not be checking each feature against local topography, and I will not be correcting typos or miscategorizations. So, there would be some inaccuracy and a small number of errors in the import. The tradeoff would be adding some 1700+ features that are currently missing from OSM.
I have written up the import proposal at B1tw153/Missing Alaskan Peaks Import Plan - OpenStreetMap Wiki and I’d be interested in any comments people may have on the proposal or opinions in favor or opposed to the import.
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Ce sujet de discussion accompagne la publication sur https://community.openstreetmap.org/t/proposal-to-import-missing-summits-in-alaska/107024