Every Macrostrat column has a footprint, in two independent parts.
- The location is where the data were gathered: a single point, with a radius saying how far off it might be, or the line a section was measured along. It is meaningful for measured sections and drill cores. A composite column has no single place.
- The region is the area the column stands for, as a polygon. It is what a composite column is, and what a measured section may also claim to represent. A measured section can have both.
The column editor's Location page edits both. Macrostrat stores a point and a polygon for each column; a line and a radius are kept with the column's data until the database has somewhere to put them.
Entering coordinates
A location point can be typed in any of the formats below. Pick the format, type the coordinates as you have them, and press Enter: the editor reads them back as decimal degrees so you can see what it understood, and places the point. All formats are read against the WGS84 datum, which is what GPS units and web maps use. Coordinates are kept to five decimal places, about a metre.
| Format | Shape | Example |
|---|---|---|
| Decimal degrees | Latitude, then longitude; south and west negative | 43.0731, -89.4012 |
| Degrees, minutes, seconds | Latitude then longitude, each ending in N, S, E or W; minutes and seconds optional | 43°04′23″N, 89°24′04″W |
| UTM | Zone, band letter or hemisphere (N/S), easting, northing, in metres | 16T 305000 4771000 |
| MGRS / USNG | Grid zone, 100 km square, easting and northing to equal digits | 16T BN 05000 71000 |
| WKT point | POINT(longitude latitude), as GIS software writes it | POINT(-89.4012 43.0731) |
Notes on each:
- Decimal degrees are latitude first, as most sources write them. The separator can be a comma, a semicolon or a space.
- Degrees, minutes, seconds accept the usual symbols (
°,′,″, ord,m,s, or none) and any separator between the parts.43 04 23 Nand43°04.383′Nare both read. The hemisphere letters are required, since they are what tells the two values apart. - UTM needs the zone number and either a latitude band letter (C to X, omitting I and O) or a hemisphere letter. A band letter is converted to the hemisphere. Eastings and northings are in metres.
- MGRS is the military grid, also used as the US National Grid. The spaces are optional. Precision follows the number of digits: ten digits is a metre, eight is ten metres.
- WKT is longitude first, the reverse of the others, because that is how the standard writes it.
The parsers come from the geodesy library, whose documentation describes the formats in detail.
Other formats, such as state plane coordinates or a projected grid other than UTM, are not read. Convert them first in GIS software, or enter the decimal degrees.
Finding a place
The search field above the location form finds places by name, using the same place index as Macrostrat's main map. Choosing one frames the map there so the point can be placed by hand; it does not set the location itself.
Exporting
The Location page writes the footprint out as GeoJSON, with the location and the region as separate features, and copies either part as WKT. A located point is also shown in degrees-minutes-seconds, UTM and MGRS.
