Engineering and Graphs :: Engauge

If you are engineer then you can merely work without graphs, you will need it in the form of hydrographs, for calculating pavement thickness, to show stress vs strain relationship, interlink two variables from research data or to choose the type of pump you will need for water supply and the list continues.

But if you need to use some printed graph to find out thousands of values corresponding to other thousands of points then definitely you are in trouble. Check one variable, strike the graph line vertically or horizontally and strike axis to get corresponding value, arghh, its hard and tedious, isn't it? Now what if I tell you that you no more need to stare at those graphs just to get corresponding values, yes now you can do graph jobs in no time, especially if you have to find hundreds of values from a single graph.

Recently I was developing a software for RWSSP - WN (Rural Water Supply and Sanitary Project - Western Nepal), the objective of which was to help select the type of pump according to requirement. Basically the pump selection was based upon the required water head and required discharge. There were choices for models from few companies from which one has to select and obviously most of those selection were to be made based on the graphs provided. First narrow down the type of pump to be used based on a graph, then choose best model available of the previously selected type.

My boss first asked me to note down coordinates of many points from the provided graph to use it in software and I was pretty much sure that doing it manually won't be an easy job. Then I plug in my N900 to pc via USB, connected to internet and googled for it. I browsed few dozen sites to see what it has to offer and finally Engauge become my ultimate choice.

"Engauge (from en "make" and gauge "to measure") verb meaning to convert an image file containing a graph or map, into numbers.": writes the developer in his site http://digitizer.sourceforge.net/. You can learn more about the software from the site while am here to provide quick and concise guide on the use of the software.

General steps to digitize your graph:
1. If its print graph, then create a scanned image of the graph.
2. Import the image to engauge.
3. Define axes and their coordinates, for this you will need three points of the axes, remember the axes or axis may be logarithmic as well (log 10 that is), just imagine how will you deal with log graphs if you have to do it manually. Use L shaped icon for that.
4. Create layers or curve list form settings>curve in case you have more than one curve on the same graph.

5. Use Grid line removal option if you need from setting>grid line removal.
6. Use segmentation fill to auto select points of the curve for particular layer. Switching layer or curve is as easy as eating pie.
7. Manually locate points in the graph if you miss many point in the graph.
8. Export points from file>export as to excel.

9. Get coordinates of all points you selected, even better in different columns if there were more than one curve.
10. Draw scattered line diagram and add trend line, now you will get something like y=f(x), so what now? If you need y just input x into the formula.

Confused??? Checkout the site and read on. The above information is not meant to be full explanation but a concise review of the software. Also read the help file of the software, its full of illustration, you will get idea in no time.

Any problems using the software? Let me know and I will try to help you.

Thank you for reading.