wgtmac commented on code in PR #494: URL: https://github.com/apache/parquet-format/pull/494#discussion_r2074683952
########## Geospatial.md: ########## @@ -162,3 +196,26 @@ The axis order of the coordinates in WKB and bounding box stored in Parquet follows the de facto standard for axis order in WKB and is therefore always (x, y) where x is easting or longitude and y is northing or latitude. This ordering explicitly overrides the axis order as specified in the CRS. + +# Special geospatial values + +A special geospatial value refers to an individual scalar value (e.g., X, Y, Z, +or M) within a coordinate of a non-`null` geospatial instance. These special +values are excluded from bounding box calculations. For example, in a +`LineString` instance with XY coordinates `[(1, 2), (NaN, 3), (4, 5)]`, the +`NaN` value on the X axis will be excluded from the bounding box calculation, +while all other scalar values will be included. + +* `NaN`: Not a Number. A `Point` with no X and Y values in WKB is + represented by a `Point` with each scalar value set to an IEEE-754 + NaN value (e.g., hex: `01 01 00 00 00 00 00 00 00 00 00 00 f8 7f 00 00 00 00 00 00 f8 7f`). + NaN values in other geometry types are typically considered invalid + geometries by other libraries. +* `Empty geometries`: Geometries explicitly marked as empty in WKB using + indicators such as `numPoints`, `numRings`, or `numGeometries`. Examples + include `LineString` with no coordinates (hex: `01 02 00 00 00 00 00 00 + 00`) or `Polygon` with no coordinates (hex: `01 03 00 00 00 00 00 00 00`). +* `Out-of-bounds coordinates`: Values that fall outside the valid range + for `GEOGRAPHY` types. For example, `x < -180` or `x > 180`. Review Comment: Should we also mention `y < -90 or y > 90`? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
