[Qgis-user] Re: Azimuth and Distance Plugin (was Re: your old qgis plugins)
Darren Cope
darrencope at gmail.com
Thu May 26 12:28:20 PDT 2011
Hi Fred,
Actually, everything does seem to be working properly, except for the
"Starting Vertex" which for some reason gets shifted.
In my example, the NW corner of the parcel should start at
604043.804336,5057981.62906 (UTM 17N, NAD83). Enabling snapping and clicking
the same corner gives 604419.326705;5057051.87503 as the coordinates, in the
Distance and Azimuth tool, while a 'numerical vertex edit' gives the proper
coordinates. However, it does not appear to be giving consistent results, as
another time it gave me different coordinates. Perhaps there's a bug in the
Select From Map function?
When manually over-riding the starting corner, everything works exactly as
expected.
You are correct that I needed to reverse the bearings in some cases to
simulate 'walking around' the outside of the parcel. That, and the
combination of 'boundary' and 'bearing' seems to be the key!
Darren Cope
http://darrencope.com
http://dmcope.freeshell.org
On Wed, May 18, 2011 at 3:40 PM, Fred LaPlante <flaplante at flos-inc.com>wrote:
> I just tried out the map you sent me and the Az & Distance plugin worked
> just fine for me. the closure seems pretty good though I didn't zoom in to
> check. I did switch the n/s and E/W designations on 3 edges so that all
> bearings were toward the next corner (moveing clockwise aroind the map).
> other that that and being careful of my typing, I did nothing but enter thee
> data.
>
> I did specify 'boundary', 'bearing', and 'feet' for options. And I did
> have CRS set to NAD83. Also I did save (or 'export') the data to a test file
> and was able later to retrieve it to correct an error.
>
> So the plug-in works for me in version 1.6.0. I suspect your problem was
> mainly in making the bearings consistent from a boundary walker's
> perspective.
>
> Fred
>
>
> On 5/18/2011 1:33 PM, Fred LaPlante wrote:
>
>> OK, looks like we are both talking about the same 'English' system of
>> metes & bounds. Your parcel looks just like mine. And none of the bearings
>> look nearly precise enough to guarantee closure. The most conspicuous
>> absence is lack of a True vs magnetic notation. For Canada that can be a
>> killer - and magnetic can easily vary 40min in ten years. Also I see that
>> the surveyor didn't enter the bearings in a consistent way as he walked
>> around the property so the bearings have to be reversed manually, or a
>> negative sign used.
>>
>> Anyway, I'll get a copy of qGis running and see what I can do with your
>> drawing.
>>
>> Fred
>>
>> On 5/18/2011 1:19 PM, Darren Cope wrote:
>>
>>> Thanks Fred,
>>>
>>> I've (re)attached the image example--the coordinates we deal with in
>>> Ontario (and most of Canada) seem to (almost all) come in the format shown
>>> in my attachment. It doesn't make a whole lot of sense to me from a
>>> 'usability' standpoint, but...
>>>
>>> Darren Cope
>>> http://darrencope.com
>>> http://dmcope.freeshell.org
>>>
>>>
>>> 2011/5/18 Fred LaPlante <flaplante at flos-inc.com <mailto:
>>> flaplante at flos-inc.com>>
>>>
>>> Wow! voices from the past.
>>>
>>> Darren,
>>>
>>> I haven't done anything with qGIS for over a year now. But this
>>> does remind me I need to get back to it again just to catch up on
>>> some things here on my desk. Unfortunately I 'upgraded?' my
>>> computer system to Windows7 since then and qGIS didn't make the
>>> transfer (though the data did make it!). So I will have to answer
>>> your questions from memory.
>>>
>>> I think Mauricio got it all right. Here in Maine, USA, land
>>> boundaries in property deeds and maps are given in 'metes and
>>> bounds' that is nnn.nn feet North/South xxdeg East or West. (For
>>> example 950.5 feet N 30deg 45Min 20Sec East). So what I would do
>>> is to establish a starting point from whatever corner I could pin
>>> down on a map and then 'walk' around the property entering the
>>> distance and heading as given on the deed or property map. I have
>>> done this with the Az & Dist plugin for many land parcels in my
>>> home town. But having said that let me add that getting 'closure'
>>> is seldom achieved. I found the accuracy of the property deeds or
>>> maps even with signatures and seals of licensed surveyors was very
>>> poor. Sometime I got definitions like "900feet N 40deg E (plus or
>>> minus)". It seems only the surveyors markers mean anything and the
>>> legal description is only a guide to help find them. Surveyors
>>> tell me "Here in Maine everyone knows how to get to their property
>>> but no one really know where it is."
>>>
>>> Unfortunately your plan didn't get to me so I can't be sure just
>>> what the difficulty is. If you could send me a copy, I will try to
>>> enter it into qGIS and see what happens. Perhaps a bug has gotten
>>> into the code since I last used it. But I still have my original
>>> plugin code so we should be able to get things working again.
>>>
>>> Here is an extract from some instructions I wrote for the local
>>> town government. Perhaps this will be helpful.
>>>
>>> Fred LaPlante
>>> Mercer, ME, USA
>>>
>>>
>>> 5.4 Survey Data
>>>
>>> Deeds normally provide a list of bearing and distance from a
>>> starting point around a property boundary in a consistent
>>> direction until returning to the start. The process describe here
>>> should accept most property descriptions as written.
>>>
>>> Survey maps may be consistent as well, but sometimes a direction
>>> my appear as a ‘back bearing’ due to the nature of the survey.
>>> These can be handled with the addition of a minus ‘-‘ sign at the
>>> beginning of a bearing.Failure to catch this detail can produce
>>> some fascinating, but useless,drawings.
>>>
>>> 1. Open or create a layer for your new feature.
>>> 2. Use properties to set transparency to 50-75%
>>> 3. Enable editing of the layer.
>>> 4. Open the ‘Azimuth & Distance’ Plugin.
>>> 5. Verify both the Layer and Coordinate System (CRS) shown are
>>> correct.
>>> 6. For most surveys, Boundary type survey is correct.
>>> 7. Select North type that applies (enter magnetic declination if
>>> appropriate)
>>> 8. Select Distance units. In USA this will probably be feet.
>>> 9. Select Angle Type: Azimuth is a compass heading, Bearing is of the
>>> form N xx deg E
>>> 10. Click ‘Capture from Map’
>>> 11. Move mouse to location of starting point on base map.
>>> 12. Under ‘Next Vertex’ enter direction and distance from survey
>>> or deed.
>>> 13. Click ‘Add to Bottom’.
>>> 14. Repeat above 2 steps as needed.
>>> 15. Click ‘Export List’ to save your entries for a later time.
>>> 16. Click Draw.
>>>
>>>
>>>
>>> On 5/18/2011 11:14 AM, Maurício de Paulo wrote:
>>>
>>> Hi Darren,
>>> I haven't worked on the plugin for a long time now.
>>> The terms are about what angle is given to the plugin.
>>> Bearing is measured from a given direction but with 180
>>> degrees for each side (Ex.: 90e means right. 90w means left).
>>> Azimuth is measured from a given direction but with 360
>>> degrees clockwise. (Ex.: 90 means right. 270 means left)
>>>
>>> The polar/Radial means that the angles area going to be
>>> centered on the point given. It's usefull when you did angular
>>> measures from the same point. It's used when you measure
>>> angles and distances from a single point to draw a curve.
>>> The Boundary means that the angles are relative to the last
>>> point you measured. It's commonly used in the descriptive
>>> documents when the next point is calculated with angle and
>>> distance from the current point.
>>>
>>> I think Fred can help more with the meaning of each term as
>>> many of them I couldn't translate to a common english idea.
>>> Fred Laplante is also involved in the project and implemented
>>> many of these concepts.
>>> Best regards,
>>> Mauricio de Paulo
>>>
>>> 2011/5/18 Darren Cope <darrencope at gmail.com
>>> <mailto:darrencope at gmail.com> <mailto:darrencope at gmail.com
>>> <mailto:darrencope at gmail.com>>>
>>>
>>>
>>> Hi Mauricio,
>>>
>>> I'm curious if you are still working on the Azimuth and
>>> Distance
>>> Plug in for QGIS? I am back to it again, and still having
>>> difficulties. I would like to be able to help you test if
>>> you are
>>> still developing. I have an example (attached) of a plan that
>>> needs to be entered using the distances and bearings shown (in
>>> that exact format). How would I go about doing so? I have tried
>>> every possible combination that makes any sense to me! I'm
>>> fairly
>>> certain I just don't fully understand the implications of the
>>> "Polar/Radial" and "Boundary", and "Azimuth" and "Bearing"
>>> settings. Perhaps you could explain?
>>>
>>> Cheers,
>>>
>>> Darren Cope
>>> http://darrencope.com
>>> http://dmcope.freeshell.org
>>>
>>>
>>> 2009/11/11 Darren Cope <darrencope at gmail.com
>>> <mailto:darrencope at gmail.com>
>>> <mailto:darrencope at gmail.com <mailto:darrencope at gmail.com>>>
>>>
>>>
>>> Hi Mauricio,
>>>
>>> I'm not 100% sure what is going on with the precision. I
>>> suspect the snapping feature will solve this, as the
>>> difference is quite small. I zoomed in to 2:1 (e.g. as
>>> far as
>>> I could) and clicked as close as I possibly could to a
>>> corner
>>> vertex, and then when I drew my feature, it doesn't line up
>>> (although the difference is minute in terms of actual
>>> distance)
>>>
>>> I guess I'm still not 100% clear on how the coordinates are
>>> entered. What does the 'zenith' column mean? I have a
>>> lot of
>>> plans that give angles relative to north or south (so
>>> they are
>>> displayed as Nxxdxx'xx"W or Sxxdxx'xx"E for example). I can
>>> convert these to a 360-based azimuth, but it would be
>>> nice to
>>> be able to enter these without doing any prior conversions.
>>>
>>> It looks like the zooming issue is fixed now!
>>>
>>> Thanks for all of your work on this--please let me know
>>> if I
>>> can provide any further information or testing for you.
>>>
>>> Cheers,
>>>
>>> Darren Cope
>>> http://dmcope.freeshell.org
>>>
>>>
>>>
>>> 2009/11/7 Maurício de Paulo <mauricio.dev at gmail.com
>>> <mailto:mauricio.dev at gmail.com>
>>> <mailto:mauricio.dev at gmail.com <mailto:mauricio.dev at gmail.com>>>
>>>
>>>
>>> Ok, thanks for the ideas. But could explain some of
>>> them
>>> to me?
>>> What happened with the precision of the starting point?
>>> I've made some tests here and the precision should
>>> be ok.
>>> I've made a teste with 0,0,0 and it drew fine.
>>> Could you
>>> tell me how to reproduce the bug?
>>> The snapping feature is my main priority now. I
>>> think this
>>> is a great improvement.
>>> DMS should be second in the list. But actually I
>>> need some
>>> inputs on how is best entered a coordinate. We're
>>> talking
>>> about azimuth here. And a DMS should have 3 numbers.
>>> Something like 10o14'52'' is possible and easy for the
>>> user. Is it ok?
>>> About the much larger extent... Hum... Fixed on zoom to
>>> selected feature. I think that should solve it.
>>> Gratefully
>>> Maurício de Paulo
>>>
>>>
>>>
>>>
>>>
>>>
>>> -- Mauricio de Paulo
>>> Engenheiro Cartografo
>>> MapeandoOBrasil <http://mapeandoobrasil.blogspot.com>
>>>
>>>
>>>
>>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20110526/d4d007b5/attachment.html>
More information about the Qgis-user
mailing list