Using a non-georeferenced coordinate system

[DylanRichardson]

Hello,

I am making a map using an image of another map. This map exists in a completely flat space, and therefore I do not want to georeference the map at all. Instead, I want to tell arcGIS to use a X/Y coordinate system that I define myself (the origin will be somewhere in the middle of the map). After doing this, I will input feature points on certain coordinates that I already have saved. However, I am having a great deal of difficulty figuring out how to create my own XY coordinate system which is independent of Earth-based projections, and I am new to GIS so any help with this puzzle would be greatly appreciated!

Thanks.

[DanPatterson_Retired]

What are the range of numbers you are using?  could you just assume for all intents and purposes that you are working near the equator south of Greenwich and treat your long's and lats or X and Ys as simple X and Y values and maybe a UTM  coordinate system spanning a larger longitudinal width .  See also the Platte Carree  (also know as equirectangular, equidistant cylindrical, simple cylindrical, or rectangular) which may suit your case.

[BenLeslie1]

I could be wrong but aren't all projected systems flat - could you just pick one and ignore its implied Earth location?

But I'd recommend picking one that matches your base units - most are in metres but the State Planes are in feet if you like things to be more difficult.

[DylanRichardson]

I should clarify: I want arcGIS to be set in the X/Y values I am using so I can add data from a spreadsheet quickly and have it appear correctly on my map. To accomplish this I don't think I can just ignore which projected coordinate system the map is set to.The units I am using are meters (approximately -2000 to 1000 horizontally and -2000 to 1000 vertically). Essentially, I am trying to get arcGIS to display the XY coordinates I want when I hover over a specific part of the image instead of whatever it has pre-defined.

I appreciate the responses!

[BenLeslie1]

Ah I think need to work the other way round and make your image fit the xy coords instead.....

So, pick a coord system, load your xy coords as points (or whatever), and then using the Georeferencing toolbar resgister the image to the coordinates.

Hope this makes sence.

[GordonKnight · Accepted solution]

To create a custom coordinate system

Open the data frame properties and click the Coordinate System Tab

Click the Add Coordinate System drop-down button and select New> Projected Coordinate System.

In the Name: box pick Local

Set the parameters to something close to where your map is located

Select the units and leave the GCS as is.

Use Go to XY to find your center and place your map and data.

Let us know if this works.