I have to develop an article entitled as "GIS IN ASSESSMENT OF BUS TRANSIT SYSTEM ACCESSIBILITY CONSIDERING GRADES". I'm still at an early stage of development of the research project, but I have realized that there are very few methods to assess the accessibility of transit networks. The academic literature bring the distance of 400 m (5 minutes walk) as the maximum appropriate distance to be traveled by the user to walk to access the network.

However, there is no method to consider the grades of the land, reaching up to 100 m, depending on the inclination.

Based on the above, with the data, the idea would be create a kind of 400m buffer around each bus stop (but considering the slopes). Then add the uncovered areas and identify the area percentage that doesn't have service (disregarding any cutting centers and the like).

I have no ideia about how do it. Somebody can give me a light?

• Grade is Slope, there's lots of posts on creating a Slope from a DEM so I wont labor that.. the key is creating an accumulation of slope as the distance from the location increases which would not be easy (but not impossible) do you have any programming skills? I think you would need to use GDAL to access the raster, read an array and calculate - not out of the box but achievable. Then you might need to consider aspect, it's easier to walk down a slope than up but a down slope becomes an up slope in the other direction. – Michael Stimson May 4 '16 at 22:05
• If when you say "accessibility" you mean by walking, you might want to look into Tobler's Hiking Function. en.wikipedia.org/wiki/Tobler%27s_hiking_function – Fezter May 4 '16 at 23:45
• Adding to Michael's comment, it seems like you want to look at the tools for terrain & flow analysis, such as the accumulation tool. – Ezra Boyd May 5 '16 at 2:40
• @MichaelMiles-Stimson thanks! I'm a advanced C programmer, but I'm a baby in GIS. Anyway, I'm looking at GDAL documentation. – Rodrigo Cunha May 7 '16 at 1:47
• As a C developer I would definitely recommend GDAL, it will allow you to (easily) read rasters into a memory block which can be accessed like an array and then write the modified array (easily) to a new dataset without messing around with binary writes and headers. Have a read of the GDAL tutorial gdal.org/gdal_tutorial.html, it explains a lot about how the objects work in C, C++ and some python. It works well for me in VS C++ but it is critical to link the additional dependency GDAL_i.lib... that should get you started. – Michael Stimson May 8 '16 at 21:44