[HN Gopher] The Most Detailed Map of US Waters That You've Ever ...
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The Most Detailed Map of US Waters That You've Ever Seen (2023)
Author : surprisetalk
Score : 169 points
Date : 2025-01-19 16:25 UTC (4 days ago)
(HTM) web link (www.esri.com)
(TXT) w3m dump (www.esri.com)
| codingdave wrote:
| The detail is impressive - it even has the little 12" wide, 6"
| deep creek that runs through my property and the neighbors
| seasonal puddle/not-even-a-pond that forms in his field after
| heavy rains.
| eppp wrote:
| It also has a lot of features that dont exist and is missing
| several that do.
|
| Pretty strange. It misses a pond that is completely obvious on
| the lidar elevation map.
| erikerikson wrote:
| I can confirm the peer message. It is missing much more
| significant water features (ponds/streams/marshes) on land I am
| intimately familiar with.
| lupusreal wrote:
| I've been looking around creeks in my neighborhood and this
| layer is substantially less accurate than the base layer it's
| displaying on top of.. Not sure what's going on with this
| data.
| rgrieselhuber wrote:
| " Water plays a central role in all our lives."
|
| You don't say.
| yuppiepuppie wrote:
| I'd be interested to know how they gathered all that data. Given
| the very detailed ponds and streams that may seem invisible to
| our daily lives, did they really send someone out there to survey
| all of it? Or is this via satellite imagery or something similar?
| maxerickson wrote:
| It's derived from LIDAR scans.
|
| https://www.usgs.gov/ngp-standards-and-specifications/elevat...
|
| I'm not sure it's their best product for elevation anymore, but
| USGS also publishes 3dep, which is a unified layer of the best
| available elevation data for the US.
| qwertyuiop_ wrote:
| It's all those "ufos" with clearly marked FAA mandated
| navigation lights.
| driggs wrote:
| From high resolution Digital Elevation Models. They first
| compute the flow direction from every pixel; from flow
| direction, the compute flow accumulation at every pixel. They
| then filter based on some threshold for catchment area, and
| vectorize the flow paths.
|
| The USGS NHD+ Users Guide includes a very detailed description
| of the technical process:
|
| https://pubs.usgs.gov/publication/ofr20191096
| SpicyUme wrote:
| Weird, just spot checking a few places I know relatively well
| I see a few issues that seem like they would show up from
| that method. I wonder if there are issue in build up
| environments? Unfortunately that link is down for me.
|
| A collection of streams go uphill in this map where in
| reality I believe they flow into an underground pipe or
| something that drains into the lake in a different place. I
| wouldn't expect the underground section to be perfect, but
| the hill the streams ascend is ~50 feet.
|
| In another place two ponds are not shown, maybe due to dense
| tree cover? I believe both have water year round, but one was
| fenced off after a kid drowned and the owners may have filled
| part of it in.
| sandworm101 wrote:
| While these particular maps may be from scans, the government
| really does send people into every little field for this type
| of thing. Between geological surveys and defense planning, I
| don't there is an acre of land anywhere in the US that hasn't
| welcomed a government surveyor at some point.
| thesuitonym wrote:
| https://www.usgs.gov/special-topics/water-science-school/sci...
| ghaff wrote:
| Relatively less detail I'm sure but Raven Maps has a beautiful
| large laminated wall map of landforms and drainage in the
| continental US.
|
| https://www.ravenmaps.com/48state-drainage-landform.html
| Mistletoe wrote:
| That's really beautiful.
| ghaff wrote:
| It really is. I just had to get everything taken off my walls
| (and the house basically emptied) because of smoke damage
| remediation. A large framed map of Boston Harbor had its
| glass broken. I may just replace it with this which is
| probably more interesting as I put things back together.
| adamtaylor_13 wrote:
| Trying to scroll anywhere on the map crashes the website on iOS.
| Not sure what that's about.
| UltraSane wrote:
| It is downloading a MASSIVE amount of data. Good stress test
| for browsers.
| MichaelZuo wrote:
| How can that be the case when e.g. chrome can handle opening
| multi-GB PDFs?
| mfro wrote:
| It appears to be streaming the data in and out to reduce
| ram load. On my desktop it was very laggy and had no detail
| for 2-4 mins and from then on I can zoom into any area and
| wait a few secs for the data to overlay. GPU usage is very
| high while rendering.
| danesparza wrote:
| Not bad. Areas like Tucson, AZ are deceptive however.
|
| The Santa Cruz "river" typically doesn't have any water in it.
| :-)
| labster wrote:
| The deception works well though. Some German POWs got a map of
| Arizona and tried to escape by rafting down the Gila River.
| Naturally all escapees were found in less than a week.
| SirMaster wrote:
| Doesn't some of this change throughout the year? Like some rivers
| only run at certain times the year. If so when is this data from?
| mfro wrote:
| There are differences in representation for the mean annual
| flow of each waterway. Read the article.
| lupusreal wrote:
| Where do they get their ground truth from? They show a lake near
| me which no longer exists, as of a few years ago when the dam was
| removed.
|
| (OSM gets this right, FWIW.)
| eppp wrote:
| Lidar and some sort of algorithm probably. It seems to work ok
| but not perfectly and depending on your area the lidar point
| cloud could be almost 10 years old.
| asdasdsddd wrote:
| Wow the inner bay area is parch dry
| novaleaf wrote:
| More detail isn't necessarily better. I own some property and
| this water map repeats the same seasonal streams that exist on
| the state's (very old) records.
|
| they should validate with satellite data or something similar.
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(page generated 2025-01-23 23:01 UTC)