Geoapplications development · UTM: False Easting and False Northing 24 Link 1 False easting False...

transcript

Geoapplications development

http://rgeo.wikience.org

Higher School of Economics, Moscow, www.cs.hse.ru

Why do we use maps? 2

Pictures from Лебедева О.А., Картографические проекции (методическое пособие), Новосибирский учебно-методический центр по ГИС и ДЗ, Новосибирск, 2000

Map projection (leads to distortions) 3

https://en.wikipedia.org/wiki/Geoid

Datum: aligning spheroid (ellipsoid) 4

Geoid/Earth surface Spheroid 1 Spheroid 2

Putting all together 5

Notes on CRS definition 6

select distinct coord_ref_sys_kind from epsg_coordinatereferencesystem

Notes on CRS definition (2) 7

# R code # Convert (lat, lon) in meters to (lat, lon) in degrees library(raster) library(rgdal) # (lon, lat) in UTM projection – units are meters utm_c = cbind(470115, 6322515) utm_sp = SpatialPoints(utm_c, proj4string=CRS("+init=epsg:32637")) utm_sp # convert to (lon, lat) in WGS84 – units are degress global_sp <- spTransform(utm_sp, CRS("+init=epsg:4326")) global_sp

Ellipsoids 8

Datum 9

https://en.wikipedia.org/wiki/Geodetic_datum

https://en.wikipedia.org/wiki/World_Geodetic_System

Coordinate systems (CS) 10

Spherical geographic coordinate system 11

Can you port that on Java from C++? http://www.codeproject.com/Articles/15659/Longitude-Latitude-String-Parser-and-Formatter

Cartesian coordinate system 12

Cylindrical Transverse Cylindrical Oblique Cylindrical

Secant Cylindrical

Conical Secant Conical Planar Secant Planar

Projections

http%3A%2F%2Fwww.nps.gov%2Fgis%2Fgps%2F04_datums_coordinatesystems_65.ppt

Projections 14

http%3A%2F%2Fwww.nps.gov%2Fgis%2Fgps%2F04_datums_coordinatesystems_65.ppt

Why a map projection matters? 15

𝑑 = 𝑥1 − 𝑥22 + 𝑦1 − 𝑦2

Equirectangular projection 16

Link 1

Equirectangular projection 17

•Link 1

The plate carrée (French, for flat square), is the special case where φ1 is zero.

UTM: Universal Transverse Mercator 18

http://www.geo.hunter.cuny.edu/~jochen/GTECH201/Lectures/Lec6concepts/Map%20coordinate%20systems/UTM%20and%20UPS.htm

Apply a custom Transverse Mercator projection to each strip (zone)

Pic 1 Pic2 Pic3

• Custom means you have a separate cylinder for each strip (zone)

• The cylinder is aligned to cross the spheroid along two lines (in red)

• Each line is 180 km apart from the central meridian of a zone

Pic 1 Pic2 Pic3 Pic4

UTM: zones 21

• International Date Line) •

UTM: zones (another picture) 22

• International Date Line) •

UTM: N & S 23

UTM: False Easting and False Northing

Link 1

False easting False northing

North zones 500,000 m none

South zones 500,000 m 10,000,000 m

Link 2

False northing – no negative y-coordinates for all locations in southern hemisphere zones (10,000,000 m is enough) False easting – no negative x-coordinates west of a zone's central meridian. Northern zones do not use false northing: their y-coordinates are naturally positive.

𝒙 = 𝟑𝟎𝟎 𝟎𝟎𝟎 𝒚 = 𝟒 𝟎𝟎𝟎 𝟎𝟎𝟎 𝒙 = −𝟐𝟎𝟎 𝟎𝟎𝟎 without false easting

UTM: distortion 25

Link 1

UTM: best practices 26

Link 1

UTM: a limitation 27

• ° °

Link 1

Universal Polar Stereographic system 28

Link 1

Military Grid Reference System (MGRS) 29

Military Grid Reference System (MGRS) 30

Link 1

NASA WW Example: MGRS Grid 31

Sinusoidal projection: very large scenes 32

Sinusoidal projection 33

http://modis-atmos.gsfc.nasa.gov/MOD04_L2/grids.html https://en.wikipedia.org/wiki/Sinusoidal_projection

EPSG database: www.epsg.org 34

Collection of CRS, CS, datum, etc.

EPSG Dataset v8.7 contains: 5821 coordinate reference systems (CRS) from EPSG:200 to EPSG:69036405 126 coordinate systems (CS), CS != CRS 678 datum 14 variants of prime meridians 4232 CRS transformations (directly from to) 1829 revisions …..

21 tables

CRS Text Formats 35

Try GeoTools, GDAL http://docs.geotools.org/stable/userguide/library/referencing/crs.html http://www.gdal.org/gdalsrsinfo.html

GDAL (gdalsrsinfo): • PROJ.4 • OGC WKT • XML (GML based) • ESRI WKT format • Mapinfo style CoordSys format • simplified, etc.

http://spatialreference.org/

raro@ubuntu-pelligrini:/mnt/hgfs/RS_DATA/Landsat8/LC81790212015146-SC20150806075046$

gdalinfo ./LC81790212015146LGN00_sr_band1.tif

Driver: GTiff/GeoTIFF

Files: ./LC81790212015146LGN00_sr_band1.tif

Size is 8191, 8271

Coordinate System is:

PROJCS["WGS 84 / UTM zone 37N",

GEOGCS["WGS 84",

DATUM["WGS_1984",

SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],

AUTHORITY["EPSG","6326"]],

PRIMEM["Greenwich",0],

UNIT["degree",0.0174532925199433],

PROJECTION["Transverse_Mercator"],

PARAMETER["latitude_of_origin",0],

PARAMETER["central_meridian",39],

PARAMETER["scale_factor",0.9996],

PARAMETER["false_easting",500000],

PARAMETER["false_northing",0],

UNIT["metre",1,AUTHORITY["EPSG","9001"]],

AUTHORITY["EPSG","32637"]]

Origin = (224385.000000000000000,6322515.000000000000000)

Pixel Size = (30.000000000000000,-30.000000000000000)

Metadata:

AREA_OR_POINT=Area

Band_1=band 1 surface reflectance

Image Structure Metadata:

INTERLEAVE=BAND

Corner Coordinates:

Upper Left ( 224385.000, 6322515.000) ( 34d27'55.58"E, 56d57'49.93"N)

Lower Left ( 224385.000, 6074385.000) ( 34d43' 3.37"E, 54d44'27.51"N)

Upper Right ( 470115.000, 6322515.000) ( 38d30'26.82"E, 57d 2'42.39"N)

Lower Right ( 470115.000, 6074385.000) ( 38d32' 5.80"E, 54d48'56.61"N)

Center ( 347250.000, 6198450.000) ( 36d33'23.03"E, 55d54'25.94"N)

Band 1 Block=8191x1 Type=Int16, ColorInterp=Gray

Description = band 1 surface reflectance

GDAL output in WKT for Landsat 8 Moscow scene

don’t worry due to font size – we are looking closer on it

just in several slides

http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html

PROJCS["WGS 84 / UTM zone 37N",

GEOGCS["WGS 84",

DATUM["WGS_1984",

SPHEROID["WGS 84", 6378137, 298.257223563,

PRIMEM["Greenwich",0],

UNIT["degree",0.0174532925199433],

PROJECTION["Transverse_Mercator"],

PARAMETER["latitude_of_origin",0],

PARAMETER["central_meridian",39],

PARAMETER["scale_factor",0.9996],

PARAMETER["false_easting",500000],

PARAMETER["false_northing",0],

UNIT["metre",1,AUTHORITY["EPSG","9001"]],

EPSG codes interpretation 37

One of the EPSG goals is to give short codes for frequent combinations to exchange metadata, below WKT could be replaced by EPSG:32637

<geographic cs> <projected cs> UTM 37 North

EPSG codes interpretation (2) 38

PROJ.4 39

The "no_defs" item ensures that no defaults are read from the defaults files. Sometimes they cause surprising problems.

http://lists.osgeo.org/pipermail/mapserver-users/2003-November/046863.html

gdalinfo -proj4 LC81790212015146LGN00_sr_band1.tif +proj=utm +zone=37 +datum=WGS84 +units=m +no_defs

Notes on WGS84 40

As you can see from the EPSG database, WGS84 may mean (in different context) different entities:

• Coordinate reference system • Datum • Ellipsoid

Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)

Wikipedia: Ellipse Wikipedia: Spheroid

Wikipedia: Ellipsoid

Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)

(2) (3)(4)

SPHEROID["WGS 84", 6378137, 298.257223563,

https://en.wikipedia.org/wiki/Earth_ellipsoid https://en.wikipedia.org/wiki/Reference_ellipsoid

Reproject (raster=R, targetCRS=CRS, options) 43

Reprojection: the process 44

http://demo.geo-solutions.it/share/OptimizingRasterReprojection.pdf

Reproject: visualization in web maps 45

Reproject use case: scenes from different projections 46

Reproject: mosaic spanning several UTM zones 47

http://www.nrcan.gc.ca/earth-sciences/land-surface-vegetation/land-cover/north-american-landcover/9152 https://en.wikipedia.org/wiki/Canadian_Arctic_Archipelago

Lambert Conformal Conic (LCC) Ellipsoid Model: WGS84

(original Landsat projection is UTM)

Reproject: why important 48

http%3A%2F%2Fwww.library.yale.edu%2FMapColl%2Ffiles%2Fdocs%2FUsing_Raster_Data.doc

Vocabulary 49

Abbreviation Full

CRS Coordinate reference system

SRS Spatial reference system (the same as CRS)

CS Coordinate system (CS != CRS or SRS)

Datum Spheroid axes and its relative position to the Earth

WKT Well-known text

EPSG European Petroleum Survey Group

OGC Open Geospatial Consortium

WGS84 World Geodetic System (1984)

GIS Geographic Information System

GML Geography Markup Language

UTM Universal Transverse Mercator

Main readings 50

Google for it

Main readings 51

http://grassbook.org/

Additional readings 52

Geoapplications development · UTM: False Easting and False Northing 24 Link 1 False easting False...

Documents