Arc GIS seems inaccurate for drawing lines of specific length?

[BeckyRozumowicz]

Hello I have recently been tasked with creating a GIS map of our building layout.

This map needs to be detailed. I need to be able to draw a line that is exactly 10 feet long for example.

I browsed online and saw by creating a verticy and hitting Cntrl L you can tell Arc GIS '10 ft' .

However, if i calculate the geometry of the line this creates via attribute table it seems to always come out larger!

10 ft becomes 12.379 something feet. Why is the calculated geometry always larger? Is there a way to fix this?

[DanPatterson_Retired]

by chance are you specifying a horizontal distance but trying to draw a line on an angle?

[BeckyRozumowicz]

No angles involved. It's all straight lines {unless it is angled and i can't tell on screen, after all, drawing a straight line with a mouse is prone to human error}

[DanPatterson_Retired]

I rarely digitize, but I keep this link handy for the version I am using ... Keyboard shortcuts that can be used while editing—Help | ArcGIS for Desktop maybe CTRL D for delta x and delta y, atleast you will be able to ensure it is straight

[BeckyRozumowicz]

Helpful for being 100% sure it is straight, however, even combining Cntrl A {which you can chose direction so, set to 0 for a straight line} and Cntrl L to set length {e.g. 20 ft} when i calculate the geometry it results in ~ 24.## ft [which is 4 feet more than it should be, and the base of my problem...]

[DanPatterson_Retired]

Ok.... what coordinate system are you using?  That is way too big to be some kind of glitch for sure.  You don't have some kind of snapping or grid environment set or is this a geodatabase thing? Best practices for using feature templates—Help | ArcGIS for Desktop is the start of the tree for creating features from templates, one warning was to ensure that the features you are creating are in the same coordinate system as the dataframe, which hopefully is results in planar space. I can't help much more, since I either digitize in x-y space or in UTM or MTM coordinates and never had issues with inaccuracies in geometry.

[BeckyRozumowicz]

I'll have to check the coordinate system being used for the data frame vs the one used for the shapefile.

It's a created shapefile, so it's not a geodatabase and i have no snapping or grid environment set up.

[BeckyRozumowicz · Accepted solution]

I appears the coordinate system between the data frame and the shapefile were different.

Presuming this was the issue i changed the coordinate system of the data frame to match.

Upon calculation of geometry of something i used Cntrl L on and typed 10 ft for the result was 9.99998

the result for 20 ft was 19.99996. Obviously this minor error is tolerable. Thanks!

[DarrenWiens2]

Are your layer and data frame in the same projected coordinate system?

[MichaelVolz]

Do you have CAD software where you can draw the features and then export these features in ArcMap to make the map?