Expanding the 1885 New Orleans OHM Map
Over the first few months of 2026, Iāve been expanding these city blocks of theĀ 1885 New Orleans OHM mapĀ (shown below) to incorporateĀ data from 1896, 1908 and 1951 Sanborn Maps.
Itās coming along rather slowly, but Iām getting better and more productive with this process as I tackle individual city blocks north of Canal Street.
First I have toĀ prepare/correct/updateĀ the 1885 map:
Convert 1885 street addresses from buildings to separate 1885 address points (since the USPS made major changes to city addresses between 1885 and 1896)
Convert 1885 specific building names and functions to separate 1885 amenity points (so that buildings are more generic over time)
Correct building locations and wall positions to match contemporary 2026 locations where they are visible. Extend the buildingās timeline if they are still currently standing.
Next, IĀ extend the 1885 map to 1896Ā (the next new point in the Sanborn maps timeline):
Create new address points to match the 1896 map
Identify and extend any 1885 buildings that also appear on the 1896 map
Add any new buildings that were built between 1885 and 1896
Add 1896 business names and functions as 1896 amenity points
Extend the lifetime of other features (roads, rails, pipelines, etc)
Complete the city block so that the 1896 map is accurate
Repeat steps 1-6 to update the 1896 map toĀ make a 1908 map
Repeat steps 1-6 to update the 1908 map toĀ make a 1951 map
Sounds easy doesnāt it! It can get very complex. My biggest challenges are: 1) Dealing with positional errors, ie. reconciling old building locations and property lines to match todayās map. 2) Too much detail of small wooden buildings, awnings/porches or aux. structures. 3) Manipulating overlapping building geometry with different start and end dates (when buildings are modified over time).
This is a portion of the latest city block (along Decatur St.) that Iām working on to update from 1885 to 1896, 1908 and 1951.Ā
While Iām doing this manually now, my hope is that specialty software can be developed someday to methodically perform these tasks more quickly and with fewer errors than I can.