[Live-demo] Natural Earth in 4.5b2

[Nathaniel V. Kelso]

Brian,

Thanks for running the clean command on the themes!

For the upcoming 1.3.1 release of Natural Earth our format is now "ne_"
prefix on each of the 10m, 50m, and 110m scale set themes.

_Nathaniel



On Fri, Feb 25, 2011 at 01:00, Brian Hamlin <maplabs at light42.com> wrote:

> Hamish-
>
>  I am just finishing a set of tables cleaned via st_MakeValid() in PostGIS
> 2.0b
> Conveniently, I renamed the tables as c10m_this_that
>  so as to no longer need the quoting..
>
> I wonder how many people use the .shp files..
> or how we should name those..
>
>  -Brian
>
>
>
> On Feb 24, 2011, at 8:21 PM, Hamish wrote:
>
>  Nathaniel wrote:
>>
>>> I'm not seeing the any geometry errors in ArcGIS (the horror,
>>> the horror) on the 10m lakes theme fresh off the website.
>>>
>>
>> Arc is not a topological GIS so it misses (or ignores) many
>> errors in the data which cause problems when the data is used
>> in other ways which demand topological correctness.
>> ([river] network analysis, etc)
>> I understand that Natural Earth is mainly focused on cartographic
>> needs, but ...
>>
>>
>>  The 1.3 version that was released a couple weeks ago should have
>>> resolved most the obvious topology errors on the themes that
>>> were ID'd to me before. If you want to run a custom repair
>>> geometry / topology script on them as they're imported to the
>>> LiveDemo system, sounds fine to me.
>>>
>>
>> Loading a fresh download of 10m-lakes.zip into GRASS GIS (which
>> is fully topological) exposes a number of errors in the data.
>> Probably most are due to overlapping areas; small sliver areas
>> resulting from those after "flattening" are appear below as
>> areas without centroids (no attributes).
>>
>> GRASS65> v.in.ogr dsn=natearth/10m_lakes.shp out=ne_10m_lakes
>> [...]
>> Building topology for vector map <ne_10m_lakes_tmp>...
>> Building areas...
>>  100%
>> 1708 areas built
>> 1472 isles built
>> Attaching islands...
>>  100%
>> Number of nodes: 2627
>> Number of primitives: 4691
>> Number of points: 0
>> Number of lines: 0
>> Number of boundaries: 4691
>> Number of centroids: 0
>> Number of areas: 1708
>> Number of isles: 1472
>> Number of areas without centroid: 1708
>> -----------------------------------------------------
>> Find centroids for layer: 10m_lakes
>> -----------------------------------------------------
>> Write centroids:
>>  100%
>> WARNING: 82 areas represent more (overlapping) features, because polygons
>>         overlap in input layer(s). Such areas are linked to more than 1
>>         row in attribute table. The number of features for those areas is
>>         stored as category in layer 2
>> -----------------------------------------------------
>> 1358 input polygons
>> Total area: 1.26155E+12 (1708 areas)
>> Overlapping area: 2.02361E+11 (82 areas)
>> Area without category: 2.39549E+10 (240 areas)
>> -----------------------------------------------------
>> Building topology for vector map <ne_10m_lakes>...
>> Registering primitives...
>> 3489 primitives registered
>> 138259 vertices registered
>> Building areas...
>>  100%
>> 1708 areas built
>> 1472 isles built
>> Attaching islands...
>>  100%
>> Attaching centroids...
>>  100%
>> Number of nodes: 3253
>> Number of primitives: 3489
>> Number of points: 0
>> Number of lines: 0
>> Number of boundaries: 2021
>> Number of centroids: 1468
>> Number of areas: 1708
>> Number of isles: 1472
>> Number of centroids outside area: 3
>> Number of duplicate centroids: 5
>> Number of areas without centroid: 248
>>
>> #extract problems to another layer:
>> GRASS65> v.extract in=ne_10m_lakes out=ne_10m_lakes_problems layer=2
>>
>> displaying that extract shows problems are all in the northern
>> hemisphere, the Great Lakes of N.America being the biggest
>> pile of red ink. (Lakes Ontario and Erie look ok though)
>>
>> a map layer created with "v.clean error=problem_areas_map" can
>> help quickly pinpoint where the problems are.
>>
>> e.g. an easy place to start looking are the finger lakes within
>> this bounding box, all of which show errors:
>>
>> north:      43N
>> south:      42:18N
>> west:       77:24W
>> east:       76:12W
>>
>> (south of Rochester-Syracuse, NY)
>>
>>
>> best,
>> Hamish
>>
>>
>>
>>
>>
>>
>
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