"Why does my profile graph show an elevation change of 11 feet over 1,111,111 feet?"
In general, profiles show the change in elevation of a surface along a line. They help to assess the difficulty of a trail for hiking or biking, or to evaluate the feasibility of placing a rail line along a given route.
A Profile Graph represents height on the Y axis and horizontal distance on the X axis. The unit of distance along the X axis depends upon the units of the projected coordinate system (PCS) of the elevation raster data. For example, if data is in a Universal Transverse Mercator (UTM) PCS, the unit of distance will be in meters; if data is in State Plane PCS, the unit of distance will be in feet (US) as shown in the following figure.
![feet-vs-_feet-copy-300x148.jpg](/legacyfs/online/388180_feet-vs-_feet-copy-300x148.jpg)
However, sometimes it might be inconvenient and hard to understand the following: The elevation changes from 1,200 feet to 1,400 feet over a distance of 400,000 feet.
This may be a little like weighing a person in ounces, or counting age in minutes…
![weight-300x143.png](/legacyfs/online/388181_weight-300x143.png)
In fact, it is more meaningful when data is displayed in the following manner: The elevation changes from 1,200 feet to 1,400 feet over a distance of 80 miles as illustrated in the following figure.
![feet-vs-_mile-copy-300x149.jpg](/legacyfs/online/388182_feet-vs-_mile-copy-300x149.jpg)
Often there is a need to display the horizontal distance on the X axis of a Profile Graph in a unit other than the PCS units of the data, so as to do a quick comparison between different units or for better understanding of the data.
Here are the steps to change the horizontal distance units (units of X axis) on a Profile Graph without changing the PCS of elevation data:
1) Open Data Frame Properties (View > Data Frame Properties)
2) Click on Coordinate System Tab
3) Click Modify
![d1-252x300.png](/legacyfs/online/388183_d1-252x300.png)
4) Select the desired units (miles, kilometer etc.)
![d2-218x300.png](/legacyfs/online/388184_d2-218x300.png)
5) Click Apply.
6) Click OK.
7) Create a new Profile Graph.
And remember, don’t weigh yourself in ounces. Consider changing the units.
Additional links:
Fundamental of creating profile graphsTarun J. - Raster Support Analyst