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docs: add research for other countries handle national DSM/DEM TDE-655 #3

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docs: add research for other countries handle national DSM/DEM TDE-655 #3

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docs: add research for other countries handle national DSM/DEM
blacha Jul 6, 2023
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docs: more data for comparisions
blacha Jul 6, 2023
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25 changes: 25 additions & 0 deletions docs/area.or.point.md
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# Area or Point

## TLDR

Toitū Te Whenua (LINZ) has decided to standardise all of it's DEM/DSM into `PixelIsArea`

## Background

Geotiff files have a tiff tag `GTRasterTypeGeoKey` that controls how to interpret pixels inside of the tiff

- `Pixel Is Point` the value of the pixel represent the point in the center of the pixel
- `Pixel Is Area` the value of the pixel represents the full area of the pixel for a 1m resolution it is 1m x 1m

When a geotiff is `Pixel Is Point` the tiff's origin point is shifted by half a pixel, as the origin of the pixel is the center of the pixel.

LINZ elevation DEM and DSM's current contain a mixture of `Point` and `Area`

From a [brief survey of other jurisdictions](./national-dem-dsm/README.md.md) they mostly all use `Area`,

Area is also consistent with how [LINZ's aerial imagery](https://github.com/linz/imagery) is stored.

## References

- GDAL RFC: https://trac.osgeo.org/gdal/wiki/rfc33_gtiff_pixelispoint
- https://www.usna.edu/Users/oceano/pguth/md_help/html/PixelIsWhat.html
33 changes: 33 additions & 0 deletions docs/national-dem-dsm/README.md
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# Other countries DEM/DSM publication

Before making recommendations on how to standardise New Zealand's DEM/DSM data LINZ took a brief look at other jurisdictions and how they standardised their DEM and DSM

The key areas to look at were

- compression - What lossless compression was most common
- size - width and height of image
- file size - how big each tile is
- storage type (Tiff/COG/other)

| Country | Name | Dimensions | File SIze | Type | Compression | DataType | Nodata | CRS | PixelIsPoint | Comments |
| :---------- | :----------------------------------------------------------------------------------------------------------- | :---------------------: | --------- | ------------- | ---------------- | -------- | ------- | ---------- | ------------ | -------- |
| New Zealand | [National Elevation 1m DEM](https://data.linz.govt.nz/group/national-elevation/data/) | 480x720 px | 1.4MB | GeoTiff | LZW | Float32 | -9999 | EPSG:2193 | Area/Point | |
| Switzerland | [swissSURFACE3D Raster (50cm)](https://www.swisstopo.admin.ch/en/geodata/height/surface3d-raster.html) | 2,000x2,000 px | 16MB | GeoTiff (COG) | LZW | Float32 | -9999 | EPSG:2056 | Area | |
| USA - USGS | [National Map 3DEP](http://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Elevation/1m/Projects/) | 10,012x10,012 px | 280MB | GeoTiff (COG) | LZW (predictor3) | Float32 | -999999 | EPSG:26910 | Area | |
| USA - NOAA | [NOAA Digital Coast LiDAR](https://coast.noaa.gov/dataviewer/#/lidar/search/) | 8,463x6,475 px | 189NB | GeoTiff | LZW | Float32 | -999999 | EPSG:2229 | | In Feet |
| Australia | [Victoria 50cm DEM](https://elevation.fsdf.org.au/) | 10,000x10,000<br>Varies | 4MB | GeoTiff (COG) | LZW | Float32 | -9999 | EPSG:7855 | | |
| Finland | [2M DEM](https://asiointi.maanmittauslaitos.fi/karttapaikka/tilausvahvistus) | 3,000x3,000 px | 20MB | GeoTiff | LZW | Float32 | -9999 | EPSG:3067 | | |
| Canada | [HRDEM - CanElevation Series](https://open.canada.ca/data/en/dataset/957782bf-847c-4644-a757-e383c0057995) | 10,000x10,000 | | GeoTiff | LZW | Float32 | -32767 | EPSG:2958 | | |
| Norway | [Norway DTM1](https://hoydedata.no/LaserInnsyn2/) | 15,010x15,010 | | GeoTiff | LZW | | | | | |
| France | [RGE ALTI 1m](https://geoservices.ign.fr/rgealti) | 1,000x1,000 | | Ascii Grid | | | | | | |
| Netherlands | [Actueel Hoogtebestand Nederland AHN3](https://app.pdok.nl/rws/ahn3/download-page/) | 10,000x12,500 | | GeoTiff | RAW (Zipped) | | 3.4e+38 | EPSG:28992 | | |
| Scotland | [LiDAR for Scotland DTM](https://remotesensingdata.gov.scot/data#/list) | 10,000x6,000 | 132MB | GeoTiff | LZW | | -9999 | EPSG:27700 | Area | |
| | | | | | | | | | | |

​Elvis - Elevation and Depth - Foundation Spatial Data

https://asiointi.maanmittauslaitos.fi/karttapaikka/tilausvahvistus

File Tested

Scotland - NN70_1M_DSM_PHASE1.tif