[HN Gopher] Lidar-based GIS map of New Hampshire stone walls
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Lidar-based GIS map of New Hampshire stone walls
Author : rob
Score : 45 points
Date : 2025-08-04 14:40 UTC (8 hours ago)
(HTM) web link (nhgranit.maps.arcgis.com)
(TXT) w3m dump (nhgranit.maps.arcgis.com)
| lemonberry wrote:
| This is neat. I see a few incorrect street names where I live,
| but also some old stone walls near where I frequently walk.
| mauvehaus wrote:
| I'm across the river from you, and my understanding is that a
| lot of the incorrect street names on online maps come from data
| sources with older names. E911 apparently caused a certain
| amount of upheaval with road names.
|
| Some of the online mapping services seem to have compromised by
| just listing all possible names for a road, whereas OnX seems
| to be working off of a different (older?) data set than nearly
| everyone.
| flipnotyk wrote:
| I used to work for a company that did GIS mapping of guard rails,
| lines, and road signs. Part of what we always ended up doing was
| massaging the data we received from the Lidar mapping to line
| things up to exact locations for clients. If this map is
| accurate, I salute whoever spent the time fixing the details.
| darksaints wrote:
| I don't have much experience with lidar, but I do with machine
| learning based approaches with photographic data. There has
| been a massive explosion in the last 5-10 years in filtering
| and processing algorithm advances that can more readily clean
| up false positives and insignificant noise. I would assume the
| barriers to high quality data are quite a bit lower now.
| jppope wrote:
| very cool project and map. I've recently picked up stone masonry
| so this is super great to view
| uptime wrote:
| I can see portions of a few walls that are out in spots that used
| to have a road over 100 years ago but now are reclaimed by the
| forest. Some of areas are densely overgrown now. Nice work.
| quesera wrote:
| I have deep knowledge of only a tiny few square miles of
| sparsely-populated mostly-forest in New Hampshire.
|
| I see both surprsing accuracy, and the occasional baffling "I
| wonder what looked dense there??" errors.
|
| So as usual, LIDAR returns non-intuitive results sometimes, and
| is ideally refined by ground research, when the budget allows.
|
| But I'll definitely check out the apparent errors in more
| detail next time I'm there. :)
| lemonberry wrote:
| I look forward to finding some of these near me too.
| mikeocool wrote:
| For folks not from New England: it's very normal to walk through
| inhabited the woods in New England and come upon a seemingly
| totally random stone wall in the middle of nowhere.
|
| Much of New England is 2nd(?) growth forest -- the original
| forests were chopped down to make space for farmland. The soil is
| incredibly rocky, and so farmers would go through there fields
| and chuck the rocks to the side, making the walls. Eventually
| people realized that New England's rocky soil was not very good
| for farming/local farming became less important as food was able
| to be transported longer distances, and much of the farm land was
| abandoned and eventually reforested -- with the only the rock
| walls remaining (or at least that's what I was taught growing up
| there).
| joshuamcginnis wrote:
| This is neat. I'm curious to know what the practical uses of this
| information are? Anyone know?
| hopelite wrote:
| My first thought is for historical research. It would be quite
| a bit of help if you have some old town or settlement map that
| you can compare to/overlay with a LiDAR stone wall map.
|
| I am not sure, but it may also serve historical preservation
| purposes if that is an issue, e.g., if administrators are
| deciding on land partitioning and/or development plans.
| teeray wrote:
| It could be used to enhance topo maps for hiking. If you're
| lost and come across a stone wall, you now know where it
| possibly leads.
| rob wrote:
| I'm not affiliated with the site I submitted, but some just
| _really_ love stone walls, especially those of us here in New
| England. I 'm part of a "New English Stone Walls" Facebook
| group that has ~65,000 members.
|
| To me (I'm in CT) there's something really cool to be in a
| forest surrounded by trees but see a perfectly made stone wall
| just there in the "middle of nowhere." I think about how much
| time and effort it took back in the early ~1800s to clear all
| that land, move all those rocks across fields without modern
| machinery, and put so much effort into constructing these
| walls. Some are over 6 feet wide and many are in incredible
| shape for being put together ~200 years ago.
|
| There's also the "Stone Wall Initiative" spearheaded by Robert
| Thorson of the University of Connecticut that also has tons of
| info:
|
| https://stonewall.uconn.edu/
|
| (He also has a really good "Stone by Stone" book available on
| Amazon.)
| PyWoody wrote:
| Tom Wessels has a great chapter in Part 1 of his "Reading the
| Forested Landscape" video series about New England stonewalls.
| [0] A common myth is the walls were built over time due to the
| rocks being pushed up by the frost but that's not true!
|
| The over 125k miles of stonewalls were built in just thirty years
| because of sheep.
|
| [0] https://www.youtube.com/watch?v=zcLQz-oR6sw&t=129s
| paleotrope wrote:
| Stone walls were built because of deforestation caused by
| clearcutting land to make sheep pastures, made wood for fences
| unavailable.
|
| Hmm I had always thought that the deforestation was caused by
| demand for wood for heating and cooking.
|
| Something about this sounds incomplete. A farmer isn't going to
| waste his time making a wall, especially the dodgy disorganized
| walls that are common in the region. A farmer doesn't need a
| shallow wall, stone or wood. The walls you come across in new
| england in the forest look exactly like people expect, a place
| on the edge of your farm to dump rocks. Now, maybe not frost
| grown, but New England has lots of rocks everywhere.
| kubectl_h wrote:
| Wessels does indeed say the stone for fences most likely came
| from stone dumps in _cultivated_ fields that were clear cut
| for crop fields and, later, the sheep craze and those rocks
| were pushed up from the ground in those cultivated fields
| over the winter.
| lemonberry wrote:
| I believe a lot of wood went to ship building too. Though
| that may be more true of forests near rivers so they could be
| floated to Portsmouth.
| rob wrote:
| If anybody is in Connecticut like me, here's a LiDAR map you can
| use for the state to find your own stone walls here:
|
| https://experience.arcgis.com/experience/4c801e35f200493ebff...
|
| ("Hillshade 2023" and "Hillshade 2023 SE illumination" are the
| two I use.)
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(page generated 2025-08-04 23:01 UTC)