[Talk-us] NHD import

Martijn van Exel mvexel at gmail.com
Mon Apr 9 07:11:55 BST 2012

On 4/9/2012 12:00 AM, Clifford Snow wrote:
> On Sun, Apr 8, 2012 at 10:39 PM, Martijn van Exel <mvexel at gmail.com
> <mailto:mvexel at gmail.com>> wrote:
>     Hi,
>     Remapping in CA, I come across some weird stuff.
>     Here's some NHD 'data':
>     http://www.openstreetmap.org/?__lat=35.17764&lon=-119.12641&__zoom=16 <http://www.openstreetmap.org/?lat=35.17764&lon=-119.12641&zoom=16>
>     Either the aerial imagery is way off here, or this is just bad data.
>     If it is, I presume that there has been a review of this data before
>     import, this is the exception, and the vast majority of imported NHD
>     objects actually do represent reality. I hope.
>     --
>     Martijn van Exel
> Are you talking about the water - lakes and ponds?  From reading
> nmixter's diary, he/she has posted comments about mapping farms.  One
> comment suggested taking the import to the talk-us mailing list. BTW - I
> did just drive through some farm land in Western Washington.  Farmers
> had dug temporary canals to help drain (or so I assumed) the water from
> the field so they could plant.  I probably wouldn't map it unless they
> were permanent.

Yes, I see a lot of water features that are just not corroborated by the 
aerial imagery, which could mean one of at least three things:
1) The aerial imagery is out of date
2) The NHD data is out of date
3) The NHD data represents something I don't understand (the future, a 
temporary situation (which should not be in OSM), something underground?)

Martijn van Exel

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