#pzmaps

[pzmaps]

Expanding the 1885 New Orleans OHM Map

Over the first few months of 2026, I’ve been expanding these city blocks of the 1885 New Orleans OHM map (shown below) to incorporate data from 1896, 1908 and 1951 Sanborn Maps.

It’s coming along rather slowly, but I’m getting better and more productive with this process as I tackle individual city blocks north of Canal Street.

First I have to prepare/correct/update 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 building’s timeline if they are still currently standing.

Next, I extend the 1885 map to 1896 (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 to make a 1908 map

Repeat steps 1-6 to update the 1908 map to make a 1951 map

Sounds easy doesn’t 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 today’s 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 I’m working on to update from 1885 to 1896, 1908 and 1951. 

While I’m 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.

[pzmaps]

Starting 1885 New Orleans with OHM

During 2024 and 2025, I spent many of my mornings sipping coffee and building out the 1885 Sanborn Fire Insurance Map in OHM. I created and tagged thousands of buildings across New Orleans. I also added as much information into OHM as I could, given the high level of detail available. Each building typically contains the following info:

Levels (number of floors)

Material (wood/brick/hard)

Street address (which were obsoleted in the 1890s)

Generic function (store/dwelling/stable/shed/lodging/etc)

Specific name or operator of a building or business

Start Date and End Date (I typically used /1885 and 1885/)

I spent about a year working on this project to create a digital version of this highly detailed 1885 Sanborn Fire Insurance Map (above) using OHM (OpenHistoricalMap.org). The digital OHM map, pictured below, has many ordinary buildings, is searchable and animated. You can see streets and buildings appear or disappear over time as you move the time slider.

[pzmaps]

Begin using OpenHistoricalMap.org

Using OSM in 2023 got me into even more fun mapping projects with OpenHistoricalMap.org. I started mapping using OHM on my town of Menlo Park. I learned to use several online sites for geo-referencing a variety of old maps.

Then I learned about Sanborn Fire Insurance Maps and started building and using geo-referenced data from OldInsuranceMaps.net.

Then I spent a few weeks in Bellingham, WA, so I did some mapping there, and then I started a big historic mapping project of New Orleans, LA in partnership with OldInsuranceMaps.net

I admit, I have a soft spot for New Orleans... it is a special place that is worth recording and preserving.

[pzmaps]

Begin using Mapillary.com

Sometime in 2023, I started using Mapillary.com for mapping street level detail, which is not visible from an OSM satellite image.

That lead me to buy a GoPro Max 360 camera and record my own bike trips across San Mateo and Santa Clara Counties. About a year and a half later, I had recorded more than 3000 miles of local streets.

[pzmaps]

Begin using OpenStreetMap.org

I started using OpenStreetMap.org in 2022 when I retired and needed to make maps for walking tours for the Menlo Park Historical Association. I’d always been interested in geography, maps and cartography so I was intrigued when I learned that I could help to create a digital map the world through this collective effort called OSM.

I started by marking historic buildings, adding missing houses, driveways, pools, parking lots and sidewalks in my neighborhood. Then I updated store data along Santa Cruz Ave, the main commercial street in central Menlo Park. Then I updated a lot of details (pedestrian crossings, light poles and trees) along El Camino. I mapped the electrical grid (poles and lines) and connected them to local power stations. 

Then I added a lot of houses, driveways and sidewalks all over the City of Menlo Park. Then I started mapping the tree canopy and urban trees around Menlo Park, because these trees contribute greatly to the quality of life in this town. I was interested to identify the big ones, the tallest redwoods and the oldest oaks. I admit it, I probably went a little overboard with the trees… :-) 

When I “completed” Menlo Park, I started mapping other buildings and communities, especially places that I would visit, like on a Tahoe ski trip, or while visiting suburban Dallas during the solar eclipse. 

Then I did a lot of mapping in the town of Seven Hills, OH where I lived as a teenager. It was really fun to re-visit all those familiar shopping malls, streets and buildings that I used to know so well. Most of it was still easily recognizable to me while looking at OSM satellite images.