<div>Hi Hamish,</div>
<div> </div>
<div>Thank you for the suggestions. v.hull is something that i had passed over before, it wont work on this occasion as the dam is boomerang shaped, but i will be sure to use it when i can. Takes a fair deal of processing out.</div>
<div> </div>
<div>For those that are interested the final result was as follows:</div>
<div>v.category option=add cat=1 step=0 type=area (this filled in my islands - as they weren't islands, just obsticales)</div>
<div>v.extract type=area new=1 list=1-99999</div>
<div>v.dissolve<br></div>
<div>Thanks,</div>
<div>Ed<br></div>
<div class="gmail_quote">2008/5/29 Hamish <<a href="mailto:hamish_b@yahoo.com">hamish_b@yahoo.com</a>>:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Edward Tomlinson:<br>
<div class="Ih2E3d">> I have a whole bunch of data from an RTK GPS. File exists<br>> as a MapInfo file.<br>> Imports into grass fine with area and centroids.<br>><br>> My problem is however, i want to create another vector file<br>
> that contains the mask or the external (an internal island) boundary.<br>><br>> I have been able to create the external boundary fine<br>> through the following.<br>> v.category (delete categories)<br>> v.category (add category as 1 for all)<br>
> v.dissolve (combine all boundaries with common category)<br>><br>> This is great and works fine for the external boundary.<br>> However there is meant to be an island in there. Somewhere<br>> along the way (i think after the second call to v.category)<br>
> it fills that island in.<br><br></div>right.<br>
<div class="Ih2E3d"><br>> Has anyone got any hints or ideas?<br>><br>> Essentially i am trying to create this vector to generate a<br>> mask for further interpolation of the point heights. I am<br>> assuming that i need this island removed (as there is no<br>
> point data for it) otherwise it is going to effect<br>> the interpolation.<br><br></div>Use v.overlay for the new and original map, operator=not, etc.<br>or other combination of operator=and etc until you get what you want.<br>
<br>another trick is "v.extract list=1-99999999" to only extract features with a cat number. (then v.overlay)</blockquote>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><span id=""></span><br><br>v.hull is another module to look at for this instead of v.dissolve.<br><font color="#888888"><br>
<br>Hamish<br><br><br><br><br><br></font></blockquote></div><br>