# Creating generic coordinate system in QGIS

So I'm new to QGIS (3.4) and haven't touched any mapping software in 15 or more years. I'm slowly finding my way around but I'm currently struggling to create a generic coordinate system for a map project of a generic world as I'm not familiar with proj4 format. I've been going over proj4 but could sure use some help in getting started. My simple generic world is as follows:

The X axis currently extends from -2045 to 2045

The Y axis also from -2045 to 2045

Z is 0 to 1000

Each X,Y unit is a meter

All I need to do at this point is define a generic coordinate system that will allow me to map simple vector data - X,Y points and later lines. Eventually I may want to work with elevation as well.

EDIT

I'm wanting (hoping) to use QGIS to make some simple maps of a fictional world that is flat, simply X, Y, and Z coordinates. Since the world is flat and not round, I don't really need a projection per se. I just need to specify that each X, Y, Z unit is a distance of 1 meter with the world extending 2,045 units each direction of a 0, 0 center point. So -2045 to 2045 X(east, west) and -2045 to 2045 Y(north, south). Also there is elevation (Z). So I need to figure out how to define a "projection" and then add vector features (points, lines, polygons) as simply as possible using X, Y, Z coordinates. Note; I won't be doing anything with elevation at this point but possibly later. I've never used QGIS and my last experience with any mapping software was some version of ArcView 3.X years ago so I'm flying blind here. I really just need to figure out how to specify my world and insert features with X, Y coordinates then make a map layout.

You can't tell QGIS that your world is flat and it measures 2045m from the center to the four cardinal points, and that its elevations vary between 0 and 1000 meters (because the minimum requirement is that a world is a body of revolution, more precisely an ellipsoid of revolution, or a sphere as a particular case).

And you don't need to do it.

Of course, since your world is flat, you don't need a projection either.

Then:

• Create a new project and tick the No projection (or unknown / non-Earth projection) option in the CRS tab of the project Properties.

Your world will be an infinite flat world, its units will be map units.

That in your world map units mean meters, or that there is an extension limit of 2045 map units to each of the four cardinal points, or that the elevations can only vary between 0 and 1000 meters, are restrictions of which only you will be conscious. Work on your map as if those restrictions were real, even if they were not.

• Create a new vector layer, make sure that it will have invalid projection.

• Make a map layout.

There is enough published documentation regarding the last items, and I don't think you have difficulty finding it. Play around with your map. If necessary, ask specifically about the task to be done, indicate what you have tried and what you can't achieve.

• Thank you! That is exactly what I was looking for and hadn't found. Now I think, if I've researched correctly, I can simply import point features by using the "Add Delimited Text Layer" to import a csv file of XY coordinates? Off to give it a try... Thanks again. Jan 15, 2019 at 1:58
• @user135124, you are welcome. Yes, you can do it. Successes! Jan 15, 2019 at 2:03
• So I set the project properties to "No projection (or unknown / non-Earth projection)" then attempted to import as above and it still asked for a CRS for the layer. I didn't see anywhere in the geometry definition a choice for none, just a list of all available CRS. Any way I try to create a layer it still requires a CRS. Unless I'm missing something. Jan 15, 2019 at 3:16
• @user135124, it seems that when you add a delimited text layer you are forced to assign it a projection. But you don't need to select one, you can also select none. For example, in the window that opens to select the CRS, choose a title, for example Geographic Coordinate System, the title, it doesn't have any Authority ID, select it and click Ok, invalid projection must appear in the list. Jan 15, 2019 at 11:20
• I played around with a custom CRS until I came up with the following that worked: Proj4: +proj=tmerc +ellps=WGS84 +datum=WGS84 +units=m +no_defs +lon_0=0 +x_0=0 +y_0=0 +k_0=1 I'm not entirely sure what I did there but it gave me exactly what I needed. I imported a cvs file with my generic coordinates including the four corners of the world and those were exactly 4090 meters apart according to the measure tool as the should be. So I got what I needed. Don't really know exactly how but it worked. lol Thanks for your help. Jan 15, 2019 at 15:04

If you don't care about any connection to the real world, you could take almost any projected coordinate system without false Easting and Northing.

You could simply use `+proj=tmerc` leaving all parameters to default.

• I tried that but still can't quite get what I'm wanting. I updated my OP if that maybe helps explain what I'm trying to accomplish. I'm a total newb with QGIS and am just trying to figure out the most simple methods of going about generating a map of a fictional, flat world. Jan 14, 2019 at 21:56
• It still looks ok to me. Jan 16, 2019 at 18:03