Problem with r.cost?

[Jianping Xu]

> 
> Hello Grassers,
>   Does anyone know why r.cost is behaving so much differently in 4.1 than
> in 4.0. The manual entry in 4.0 makes sense, but after using 4.1 r.cost,


Several reasons:
	1. 4.0 r.cost figures the cumulative_cost for a to_cell by simply adding
	   its cost to the from_cell's; while 4.1 r.cost does it
	   by adding the average_cost of the 'from' and 'to' cells to the 
	   from_cell's cumulative_cost.
	2. *Absolute* cell resolutions are taken into accout by 4.0 r.cost 
	   ('normalized' to 100m), not by 4.1 r.cost. 
	3. 4.1 r.cost takes more 'neighboring' cells into accout as your 
	   request, while 4.0 r.cost doesn't. And ...

Jianping Xu 
jianp at ocean.rutgers.edu


> I get this result (from the Spearfish data set):
> 
> 
> r.cost in=slope.sm ou=slope.sm.cost coor=594455,4915055
> 
> 
> slope.sm
> 
> north: 4915190
> south: 4914890
> east: 594590
> west: 594290
> rows: 10
> cols: 10
>  30  30  26  25  27  25  22  12   9  22 
>  32  31  26  23  22  17  10  11  21  30 
>  33  30  25  19  14   6  14  22  29  35 
>  30  27  22  13   3  12  21  27  33  36 
>  25  25  15   5  13  22  26  28  32  34 
>  23  23   9  15  22  27  27  27  30  31 
>  23  20   7  18  22  26  25  26  28  29 
>  27  23   5  17  20  22  21  23  24  24 
>  29  27  13  13  21  24  23  21  20  22 
>  28  28  23   8  16  24  27  28  26  26 
> 
> 
> slope.sm.cost
> 
> 135 105  87  76  67  57  51  51  60  75 
> 123  92  65  52  44  36  35  46  62  87 
> 105  79  53  33  26  24  34  52  74 101 
>  92  63  42  26  18  17  30  54  84 119 
>  78  53  33  23  18   0  24  51  81 114 
>  72  49  33  33  31  25  35  61  90 120 
>  75  54  41  50  53  51  61  72  99 128 
>  86  61  47  58  74  75  84  95 107 131 
>  98  70  56  60  77  98 106 113 125 140 
> 109  85  74  70  80 100 126 138 147 158 
> 
> Any help is appreciated.
> ------------------------------------------------------------------------
> Rick Thompson-   Research Assistant           E-mail: rick at cast.uark.edu
> Center for Advanced Spatial Technologies      Telephone: (501) 575-5736
> Ozark Hall Rm. 12                             Fax: 575-3846 
> University of Arkansas              
> Fayetteville, AR 72701
>