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I have downloaded sample tile from

http://sentinel-s2-l1c.s3-website.eu-central-1.amazonaws.com/#tiles/10/S/DG/2015/12/7/0/

and found tileInfo.json file with the following information

"tileGeometry" : {
    "type" : "Polygon",
    "crs" : {
      "type" : "name",
      "properties" : {
        "name" : "urn:ogc:def:crs:EPSG:8.8.1:32610"
      }
    },
    "coordinates" : [ [ [ 399960.0, 4200000.0 ], [ 509760.0, 4200000.0 ], [ 509760.0, 4090200.0 ], [ 399960.0, 4090200.0 ], [ 399960.0, 4200000.0 ] ] ]
  },

It appears, that tile is strictly rectangular in some coordinates, because corners contain duplicate values. Is this property constraint, i.e. true for all tiles?

What units are used for these coordinates? I tried to interpret them as lat-lon multiplied by some factor, but probably failed (was unable to identify any ground details with compre to google maps).

Also I can interpret it as meters, because they have 6 digits and meters should have 5.

UPDATE

I have plotted coordinatesenter image description here

Both height and width are 109800 of units, so it can't be meters, which would sum up to 100000. But it coincides with the number of pixels in tile.

5

If you check this page, you will notice: For Level-1C and Level-2A, the granules, also called tiles, are 100x100 km2 ortho-images in UTM/WGS84 projection.

I guess the easiest way to get insight in tiles is to download a tile KML and open it in Google Earth or similar.

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  • So, what is the unit? 509760.0 can't be number of meters inside 100 km image, because it is more than 509 km.
    – Dims
    May 18 '17 at 19:10
  • te unit is meter. UTM has a false easting of 500000m
    – radouxju
    May 18 '17 at 19:13
  • @radouxju how do you know the unit is meter? What it origin of these meter coordinate system? See my update please.
    – Dims
    May 18 '17 at 19:42
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In the properties of the tile you can find the EPSG Geodetic Parameter Dataset. This tile is in the coordinate reference system (CRS) EPSG:32610, this means that it is using UTM Zone 10N coordinates. This link provide more details about this EPSG: https://epsg.io/32610

"properties" : {
        "name" : "urn:ogc:def:crs:EPSG:8.8.1:32610"
      }

The coordinates in UTM are composed by two numbers, both in meters [ Easting, Northing ].

The first, with 6 digits is the distance from the center of the UTM Zone Central Meridian, starting in 500000m. A point in west of the Central Meridian is 500000m minus its distance in meters from it and a point in east of the Central Meridian is 500000m plus the distance from it.

The second with 7 digits is the distance from the Equator. A point in south is 10000000m minus its distance in meters from the Equator and a point in north is 0 plus the distance from the Equator.

enter image description here

Image from: https://www.maptools.com/tutorials/grid_zone_details

Here is a nice guide to UTM Coordinates: http://geokov.com/education/utm.aspx

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I found an answer here: https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system#Locating_a_position_using_UTM_coordinates

Is says, that each UTM zone has it's origin at intersection of central meridian of the zone and equator. The units are meters indeed. But the values are shifted by some big numbers to avoid negative values.

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  • 1
    this is what I said : false easting of 5000000m
    – radouxju
    May 19 '17 at 7:49
  • @radouxju yes but I was unable to understand it w/o knowing the answer
    – Dims
    May 19 '17 at 8:18

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