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Date: 2016-12-01
Document version: 1.1
Product description:
GSD-Elevation data, grid 50+ nh
LANTMÄTERIET
2016-12-01
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Table of contents
1
General description ............................................................ 3
1.1
Contents ............................................................................................... 3
1.2
Geographic coverage ............................................................................ 3
1.3
Tiles ...................................................................................................... 3
1.4
Reference systems ................................................................................ 4
2
Description of quality ......................................................... 4
2.1
Data capture and grid production ......................................................... 4
2.2
Currency ............................................................................................... 4
2.3
Quality .................................................................................................. 4
2.3.1
Positional accuracy ................................................................ 4
2.4
Metadata............................................................................................... 4
3
Data access and contents ................................................... 5
3.1
Format .................................................................................................. 5
2016-12-01
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1 General description
GSD-Elevation data, grid 50+ from the new national elevation model contains
ground height values at the intersections of a 50 m grid. The product can be used for
rough analysis and visualization.
1.1 Contents
The product consists of height values with two decimals in a raster grid with a resolution of 50 metres.
1.2 Geographic coverage
GSD-Elevation data, grid 50+ is nationwide. However, the production of the national
elevation model is not yet complete but the grid will be completed as the productions
continues.
Production of the national elevation model can be followed at Lantmäteriets homepage. See www.lantmateriet.se/geolex, under Höjddata.
1.3 Tiles
The elevation data files are in index tiles of 100 x 100 m and they are divided according to Swedish counties. Some files extends over the county border, so if several
counties are downloaded, those files will be included more than once.
Index tiles of 100 x 100 km.
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1.4 Reference systems
In plane: SWEREF 99 TM
In height: RH 2000
2 Description of quality
For detailed information about data capture, production and quality of data used to
produce the 50 m grid, see the document Quality Description of National Elevation
Model, available at www.lantmateriets.se.
2.1 Data capture and grid production
A national elevation model is produced during 2009-2017 using airborne laser scanning. A grid with 1 m resolution is produced by linear interpolation in a TIN (Triangulated Irregular Network), constructed from laser points representing ground and
water. Grid 50+ is based on this data set.
A 5 m grid is interpolated from the 1 m grid, then 10 m from 5 m, 20 m from 10 m,
and finally 50 m from 20 m. Bilinear interpolation is used for this interpolation. This
chain of interpolations means that every height value is representative for a larger
area than if the 50 m grid was produced by selecting heights directly from the 1 m
grid.
2.2 Currency
Frequency of updating is yet to decide.
2.3 Quality
2.3.1 Positional accuracy
Standard error in height in a moderate hilly landscape is about 1 m. The maximum
error can however be many times larger. Errors increase in strongly hilly landscapes.
The stepwise method of creating a more and more sparse grid has the effect that the
landscape is smoothed: high peaks will be lower and deep valleys shallower.
2.4 Metadata
A shape file with date of laser scanning can be downloaded from the ftp-site, stored
in a separate folder (see below).
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3 Data access and contents
Data can be downloaded from a ftp-site under Open data on Lantmäteriet’s homepage: www.lantmateriet.se.
The data folders are divided according to Swedish counties. There is also a folder
with data for the whole country (as far as there are data).
Metadata files will be found in a separate folder. This product description can be
found at www.lantmateriet.se.
The file name consists of the coordinate of the lower left corner, indicated at 100 km.
Example: nh_64_4.tif
Below is an example of file names after being downloaded:
3.1 Format
GSD-Elevation data, grid 50+ is available in GeoTiff format. More information about
GeoTiff can be found at: http://trac.osgeo.org/geotiff.
Height values are represented by floating-point numbers and the files are compressed with Deflate. Height value represents the entire area of the pixel (50 x 50 m,
PixelIsArea).
The following tags are used for georeferencing and for defining no data values:



ModelPixelScaleTag (33550)
ModelTiepointTag (33922)
GDAL_NODATA (42113)