Cost Distance in IDRISI

what makes cost distance more handy than in common Euclidian Distance?. See the two pictures below.

the euclidian Distance only measure direct distance from one point or object to another, regardless the morphology of the area both as a barrier or as a easiness. Best thing to explain it is with example. suppose you are in building A in the 11th floor, you friend is on the other building B on the 11th floor next to Building A with the distance of , say, 20 meters. In Euclidian Distance, it only measures the direct distance between you and your friend which is 20 meters. In reality, you have to move down , taking the stairs, elevators, or lift, walk, and take stairs in building B to meet your friend, with the total real distance, say 250 meters.

In cost distance, it calculates the friction in it process. in IDRISI Cost Distance module, first you have to have a raster point mentioning your center of object, this is the point where the distance will be measured. and the second image is the raster image of friction surface. To have friction surface, you have to convert your surface either land use or road into the friction classes.

what is friction classes? suppose i use road as a friction image. We have highway, arterial , collector, railways, and others road. How we put our new classes? suppose you want to travel as far as 100 km. If you travel in highway road, you will reach your end point in 1 hour, assuming your velocity is 100 km/hour. If you travel on arterial road, it takes 2,5 hours with velocity 40km/h. and in collector, say 3,5 hours, and others road 5 hours. ONE thing that we take it carefully is friction classes for non-road, which is in reality is the land. We can assumed as foot walking velocity which is 5km/h, so in our case, we will reach 100km after we travel for 20hours.

all this time will be our FRICTION COST. highway 1 (base cost), arterial (2,5), collector (3,5),,,,,,, bare soil (20)

we save it in AVL type of file, and run the wizards.

for my area, it was about 4 hour to run this process. I did it 3 times iteration, so,,,12 hours.

the first unit displayed in the output is in GCE unit (I forgot the abbreviation). the thing is, 5 gce means if you travel by your base situation (in highway) in certain time, you will reach 5 cells. In my case, to take 100km, it needs 6666 cells. if I assume my velocity in highway is 100km/h, this means 6666cells/60 minutes. 1000cell per minute. I use SCALAR to convert the unit of GCE into minute

happy is you can response it

pop up idea

sometimes while i’m working on my thesis, read the articles, i found a nice idea about something. today, i got an idea about ,again, how to use kriging in spatial planning.

i was reading articles from, I forgot, he write something about gis and multicriteria decision makin in vector based mode in one of the area in sao paulo brazil. it just came across into my mind that actually what he did was still taking too much time. He collected about 13 criteria to asses which municipal districts have the best quality in supporting its citizen life. But to take these 13 criteria, he has to do it manually by doing survey to random houses in one district.

so my idea is, how about if we only take smaller number of sample,,and then interpolate it,,each criterion we interpolate,, using kriging. and afterwards, we aggregate them again with their formula *overlay AND OR with some weight*

i dont think this method was used elsewhere in spatial planning. I got curiosity about this, and i try to find it in web of science,,taadraaa,,, i  didnt  get any  articles discuss about the kriging methods for interpolating social characteristics. they mainly used for *how they call it* nature phenomena such as in soil survey, forest, plant density, and recently population density.

i dont know exactly what is/are the burden of not using kriging. Or only me? yeah,,sure,i really want to know it more.