How accurate are Topo maps?

robren · Jun 11, 2016

Hi Gang

Pouring rain and 55 in beautiful NH.

I have a part-time job on a property that has a house that is dated 1792. I am doing some research with the Historic Aerials website using the topo maps and the slide feature provided. This house is not showing on the maps available from 1927 - 1968. Then there is a 16 year gap, with the next map being 1984. It does show on this map. I asked the property manager if the house had been moved to this location. He said he didn't think it had. The house is a 2 story, 10 room Colonial. It has a stone foundation under 1/3 of the house. The other 2/3 has had a full basement dug and concrete foundation placed to accommodate modern utilities.

Do you think this house has always been located in this spot and just never recorded on the topographical maps? How does that happen? I'm working up the nerve to ask if I can do a scan around the house, just to see if there are any targets.
Thanks for your input on this mystery.

remmy · Jun 11, 2016

I often wonder how accurate historic aerials topos are too. Try historicmapworks http://www.historicmapworks.com/ See if they have your area in any old maps. They have PA in 1875 atlas and maybe your area too. If so you can use the free overlay option to do basically the same thing as the slide on historic aerials.

Big Treble · Jun 11, 2016

Good question, I've overlayed old play pages over google earth and was surprised how accurate they were, obviously this was due to the survivors. I'm guessing the older topos were too.

robren · Jun 11, 2016

Thank you for that website remmy. Looks similar to historic aerials, but I like using them.

I've never seen a topo map that is NOT accurate, so this surprised me. This is a big house, and I'm wondering how it was omitted until 1984.

Garbagepicker · Jun 11, 2016

Old topo maps are not entirely correct. I myself have the same situation. The house I live in is from the early 1800's. It does not show up on a topo until the 1930's. I know that the house was there in the 1800's due to the deed and property records and it being passed down in the family. In my case my house is at the end of a dirt road and the only structure on the road. Even today one could easily go right pass the road I live on just thinking it's a farm road leading into the woods and cow pasture. It wasn't until the 1980's that the road I live on was given a name. Don't count on old topos to be the Gospel as they didn't have satellites and GPS back in the day.

NC_Digger · Jun 11, 2016

See if it's listed on this site. It's a listing of state historic places. Not finding doesn't mean it's not historic but finding it will confirm it is.

https://www.nh.gov/nhdhr/programs/documents/rpt_sr.pdf

BeepBeepBeep · Jun 17, 2016

robren said:
Hi Gang

Pouring rain and 55 in beautiful NH.

I have a part-time job on a property that has a house that is dated 1792. I am doing some research with the Historic Aerials website using the topo maps and the slide feature provided. This house is not showing on the maps available from 1927 - 1968. Then there is a 16 year gap, with the next map being 1984. It does show on this map. I asked the property manager if the house had been moved to this location. He said he didn't think it had. The house is a 2 story, 10 room Colonial. It has a stone foundation under 1/3 of the house. The other 2/3 has had a full basement dug and concrete foundation placed to accommodate modern utilities.

Do you think this house has always been located in this spot and just never recorded on the topographical maps? How does that happen? I'm working up the nerve to ask if I can do a scan around the house, just to see if there are any targets.
Thanks for your input on this mystery.

FWIW...topo maps are and were intended to show the features of the land. I've seen many cases where man-made features (especially structures) were just overlooked/not added.

How accurate are Topo maps?

robren

remmy

Big Treble

robren

Garbagepicker

Full Member

NC_Digger

Elite Member

BeepBeepBeep

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