COORDINATE SYSTEMS

For projects where you work alone, you may not be too concerned with coordinates. However, you must still draw within that 5 km drawing board.

For projects where you collaborate with others (even with those on your team at your office), at the very least, you want known X, Y, and Z coordinates.

If you want to georeference your document, you MUST have a known coordinate system and known longitude and latitude. For BIM projects, this is compulsory (though sometimes overlooked). 

If a known coordinate system has not been explicitly provided, ask for one. Otherwise, it may be up to you to decide what it will be.

Having a known coordinate system in everyone's files makes collaborating (and even internal referencing) so much easier.

WGS 84
The WGS 84 system includes an ellipsoid that approximates the shape of the Earth and a coordinate system that uses latitude and longitude to define locations on the Earth’s surface.

Pseudo-Mercator
The Pseudo-Mercator projection translates the ellipsoidal surface of the Earth into a flat map. However, for simplicity, it treats the Earth as a sphere rather than an ellipsoid.

CRS
The Coordinate Reference System (CRS) defines how coordinates relate to real-world locations. It consists of a datum, a coordinate system, and sometimes a projection.

EPSG Code
The EPSG code provides standardized identifiers for specific CRS configurations.

Projection File
Projection files contain georeference data. You can use them to load the relevant information for your project. They are often used with Shapefiles.

Common Coordinate System
A common coordinate system is a CRS that is recognized and supported by many GIS and mapping applications.

Well Known Text
WKT is a text markup language for representing vector geometry objects, spatial reference systems (CRS), and transformations in a readable format.

Geographical Coordinates
The latitude and longitude coordinates.

Geographical (WGS-84) Coordinates
The latitude and longitude coordinates using the WGS-84 ellipsoid projection.

Cartesian Coordinates
The X, Y, and Z coordinates. The Cartesian coordinates can be used for situations such as projects using the British National Grid.

ⓘ If you have georeferenced your file with geographical coordinates and things are off, but only by a few meters rather than kilometers away, try again with the other option.

Many countries have multiple possible systems that can be used. The United States, in particular, tends to have multiple per state. The UK, however, tends to use just one, so for ease of demonstration in this course's examples, we will use the following.
EPSG: 2770
CRS Name: OSGB 1936 / British National Grid
Units: metre
*Of course, for your own projects, you need to find out which one you should use.