World building using ArcGIS

[loogie]

well, if you point out the quick starts i'll take a look and see what i can figure out... i couldn't even turn it on when i looked at it (not that i tried very hard)

it does look promising (acctually better in some respects then a lot of other program i've seen) and of course.. free would make it an amazing addition to a roleplaying cartographers arsenal.

[su_liam]

Here is one good site. I still can't get my own images imported, but at least I've been able to play with Spearfish...

[loogie]

sorry man, i can't even get grass to run

no progress with arcgis as well.. i've been to busy with school..

working on a project that was due this morning at 8am...

oops... once everything slows down i should be ok tho...

[priggs]

GRASS. I get excited every time I read about it, download it, and try to use it... too painful!

[su_liam]

I got frustrated and went back to playing with landserf. Not as capable, but at least I can import my #$@ing pngs and use them as HFs. My original intention was to use landserf to see if I could convert a png HF into something GRASS could see, but I couldn't face the ordeal and played some with landserf's feature extraction and such.

I'm really interested in these flowmaps, so I'm working on a q and d java implementation of a "flowmap." I'm not sure if it's technically a flowmap, it basically just sets the value of each pixel equal to the number of pixels that are directly above it(ie those from which water could flow into it.) I have three models: Greatest Drop('Water' only flows down to the lowest neighbor below a high point. Possibly analogous to SFD?), All Drops('Water' flows to all neighbors below a high point. One possible analog to MFD, perhaps?), Scaled Drop('Water' flows into all neighbors below a high point in a quantity proportional to the change in altitude. That is steeper paths will get more 'flow'. Another possible analog to MFD?) Applying a threshold to the resulting, "flow map," could be used to give a fairly decent idea about rivers. I assume this isn't really a flowmap in the sense GRASS uses the term, because the GRASS flowmap is deadly slow and this should be pretty quick. Initially I thought I'd have to implement a heap to get best performance, but it looks like it would be O(n log n) time whether I use a heap-based priority queue or just sort cell coordinates by height initially. I'm leaning toward the sort-and-go method, because my head just refuses to wrap itself around the bottom up method for building the heap.

It's a sign of how much fun I've had trying to get GRASS to work that I'd rather program my own solution :-)

[loogie]

well arcgis is much simpler to use.. and i'm assuming most of whats in grass is the same if not copied off ESRI (they're the largest, and most used GIS software providers in the world... and i'm working for them! WOOT!)

though i don't know much about the math involved, i know the flow accumulation processes in arcgis have 2 main steps... you must create a flow direction grid(raster) which does what it sounds like you suggest takes every cell in the grid, and finds out which direction water would flow off it (N S E W + diagonals). that takes a short bit of time (i upped my anti in my map and made a new one thats 4096x4096) and in my example it takes about 2-3 mins... the result... isn't all that good for determining rivers (i guess it depends how you display it) but then you run the flow accumulation, which (from what i can disern) will go through the raster cell by cell and total those directions... so as one raster flows into another the next value is 2, the next is 3 etc etc... that takes a long time... i started running it about 10 mins ago now and its still going... last time i did it on a raster less then half the size i left and had some food, before coming back

those tasks don't seem terribly difficult to preform (generally most GIS is simple, its just that by hand it would take forever, by a computer, its fast) but the other thing that makes arcgis' tools so great is their options, for instance, flow accumulation can be weighted, meaning you can add acctual precipitation data to the formula, and get fairly accturate water fall results... as well as do other things (thats the only thing i could really think of)

the GIS tools will definitely help with many aspects, from finding trails, viewsheds (thanks for the ideas, never thought of em!) as well as doing climate modeling, and finding the best locations for various plants and animals.

now, if i only had the time to acctually do it

[priggs]

You're not alone in preferring to program rather than try to learn GRASS. I do all my spatial modeling using a combination of Python/Numpy/GDAL/OGR/Shapely/SQLite. I liked Arc/Info and ArcView 3.2, but not ArcGIS. Even though I have a copy on a Windows computer in the lab, all I use it for is to look at maps and export them to Adobe Illustrator as soon as possible. I'll quit using it totally (except probably for teaching, can't find a way out of that yet) as soon as either Quantum GIS is further improved or I finish programming my Mac GIS visualizer.

[loogie]

Well I did some more work on it... just playing around really, just seeing what i can do...


This is a sample hillshade from my new raster (much higher resolution)

After going over it visually, I preformed the same flow dir and accumulation tools


As you can see, the dir is almost the hillshade, making it much nicer to look at... at lower resolution its hard to see what this even does.


Heres the new flow accumulation.

The accumulation is more of a guildline.. all the lines shown here aren't suitable for rivers, they're mearly where water would collect (meaning drainage)... most of these lines would not even appear as a river in real life, just a path the water follows when it rains... being that these are fudged rasters and the analysis can't be 100% there are plenty of errors and such... but it gives you a good idea how to plan your rivers (and lakes)


Here you can see i've began building the rivers and lakes, i use the drainage layer, hillshade, and contours as guides, and do general outlines where i believe lakes and rivers should go... there are a lot of landlocked lakes here as well, but in real life there are a lot as well. This isn't an exact science, i just wanted it to make more sense then a fractal landmass, randomly generated with mountains and valleys exploding out of everywhere. So i've quickly traced some lakes and rivers (i may go back and do a better job, depending on how it turns out, maybe even just smooth these)

Anways, thats enough for now, i gotta get to school

[loogie]

i've been using python a bit recently in class, and my coop will be pretty much all python as far as i know.. and i've begun to like it, its quite simple and the learning curve is through the roof...

i acctually like arcMap and arc gis, and its mostly because i've like ESRI as a company for a long time, they've been good to me in opportunity, support, and friendliness... but if your a mac boy, i understand the issues there...

the new software everyones talking about is called manifold... its MS friendly, but dirt cheap... (245 for a full pro license)... and apparently has a lot of features... so its cheap.. till you learn that its not very user friendly, and to get ANY support on it costs a lot of money... we're talking 30 per email, and 125 for a half hour phonecall... and thats per issue, so if you have multiple ones your paying for more... also, they are probably the cockiest company i've every seen.. if you look at their website its full of words like "the ultimate" and "worlds best"... they even say "it blows away the competition!" and "none of the other systems even come close!" and the funny bit is that its nothing special. they have nice looking pics of their maps, cause they got pros to make em.. and i recently did a project that required us to recommend a GIS service, and it required web servers. and well. if you look at the examples of web servers for manifold... they are terrible.. like simple java based screencaps that update based on what button you press...

thats enough ranting i guess

[Redrobes]

...and the funny bit is that its nothing special.

I couldn't comment a great deal - not having used it. But I do know that (im pretty sure right now) is the only full app in existence that is using the new nVidia CUDA interface as a math extension (not DX10 or physics) which can leverage a lot of extra power from your PC. MeDem have been hot and cool over CUDA for about half a year. It was 'cool' until last week until the GX2 card was released and its warming again... I don't have any involvement with them but I know what you mean about their personality... nothing short of obsessive MS fanbois (Probably undeservedly harsh there heh heh) But heck, they have achieved a feat in programming for CUDA so I give them that respect.