shrug-l: Question du jour
Joe Noble
jnoble@ttrs.org
Fri, 30 Sep 2005 13:06:20 -0400
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I would like to suggest some sort of protocol that folks post their =
question, once, then those that have a possible solution contact the =
person directly not numerous e-mails to the entire user list. After a =
solution has been decided, the original person posting the question =
could sum the solutions in one e-mail back to the board. Sorry but my =
e-mail has been looking like a GIS chat room as of late. Joe
=20
Joe Noble=20
GIS/IS Coordinator=20
Tall Timbers Research Station
850-893-4153 x-232
=20
________________________________
From: shrug-l-admin@lists.dep.state.fl.us =
[mailto:shrug-l-admin@lists.dep.state.fl.us] On Behalf Of Sykes, John
Sent: Friday, September 30, 2005 12:41 PM
To: Geographic Systems LLC; shrug-L@lists.dep.state.fl.us
Subject: RE: shrug-l: Question du jour
=20
That's a good website. From it I gather that if I want BOTH the =
distances and azimuths to my sampling locations from the site center to =
be the most accurate, the Azimuthal Equidistant projection is the best =
solution.
=20
I came up with part of the rest of your solution on my own, however, I'm =
having trouble rotating it through 360=B0.
=20
Another solution I thought of, is setting up the sector lines in an =
AutoCad file, then importing it into my map with a world file using the =
center point and the intersection of the first radial with the 10 mile =
buffer ring as the two points.
-- John=20
=20
=20
________________________________
From: Geographic Systems LLC [mailto:info@geographicsystems.com]=20
Sent: Friday, September 30, 2005 12:19 PM
To: Sykes, John
Subject: RE: shrug-l: Question du jour
Hi John,
=20
I will try to address the first part of your question (drawing lines out =
10 miles at 11.25 degree increments) and the last part (projections). =
The second part of your question (rhumb line from site point to sampling =
location) may require more research.
=20
Projections - definitely play a part in spatial accuarcy. My guess is =
you want a projection that preserves direction and distance. A good =
place to start is the summary tables at the bottom of the map projection =
poster, http://erg.usgs.gov/isb/pubs/MapProjections/projections.html.=20
=20
Drawing lines of specific distance and angle. You can do this manually =
when you sketch a line. With Task set to Create New Feature and Target =
your line feature class, click the sketch tool (pencil) and click on the =
first point of your line. Then right click away from the sketch and =
select "Direction" (or CTRL-A) specify an angle (0 being horizontal - ie =
"11.25") and then right click away from sketch again and select "Length" =
(or CTRL-L) ie "2mi" ("mi" for miles). Or you can enter both the first =
time you right click by selecting "Direction/Length" (or CTRL-G). Check =
out online help for "Creating segments using angles and lengths".
=20
Miguel Garriga
Geographic Systems, LLC
www.geographicsystems.com
407-261-0451
cel 321-279-6019
________________________________
From: shrug-l-admin@lists.dep.state.fl.us =
[mailto:shrug-l-admin@lists.dep.state.fl.us] On Behalf Of Sykes, John
Sent: Friday, September 30, 2005 10:21 AM
To: shrug-L@lists.dep.state.fl.us
Subject: shrug-l: Question du jour
=20
Since we (collectively) solved the question I had yesterday, here's a =
new one (put on your thinking caps - this one's tougher!).
Problem=20
When establishing environmental sampling locations around a site, we =
like to ensure that the various distance buffer rings are evenly covered =
(e.g., in this case: "site boundary" to 2 miles, 2 - 5 miles and 5 - 10 =
miles. This is simple to create and check with the standard multiple =
buffer tool in ArcToolbox.
However, we also like to check that the 16 compass sectors around the =
site have also been evenly covered*. These 22-1/2=B0 sectors are =
centered on N, NNE, NE, ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, =
NW and NNW.
So, what I would like to do is to create these sectors visually, by =
drawing a line from the origin (an arbitrary "center" point on the site) =
out to 10 miles starting at 11-1/4=B0 compass heading, then rotate =
around 22-1/2=B0 and draw a line, until the 16 sectors are visually =
defined.
Any suggestions as how this can be done (easily)? Previously, when =
doing this in AutoCad, I used a radial copy command. I haven't noticed =
a similar command in ArcGIS.
Finally, once the sampling location is selected (and the lat/long of =
that location determined), we need to be able to determine and list the =
distance and azimuth (rhumb line) from that arbitrary "center" point on =
the site to the sampling location and put it into the sampling location =
attributes table (in the past, I've done this using the NGS "Inverse" =
program [fudging the rhumb line from the great circle azimuths] using a =
batch file input/output) for atmospheric dispersion modeling. However, =
I don't see any easy way to do this with ArcInfo (especially on a batch =
file basis). Any suggestions?
Finally, food for thought -- How does the projection being used effect =
the accuracy of all of this? Normally we use Albers (equal area) or =
Mercator (which gives the most accurate rhumb lines), but is there a =
better projection to use to obtain accurate distances & azimuths? I =
understand from the reading I've done that these functions may be rather =
projection-sensitive.
-- John=20
*Sometimes if there is a prevailing wind bias, we'll bias our sampling =
locations to that prevailing wind direction, but in the current case =
there is no strong prevailing wind direction - the annual wind rose =
shows an almost random 360=B0pattern.
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<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>I would like to suggest some sort =
of
protocol that folks post their question, once, then those that have a =
possible
solution contact the person directly not numerous e-mails to the entire =
user
list.=A0 After a solution has been decided, the original person posting =
the
question could sum the solutions in one e-mail back to the board.=A0 =
Sorry but my
e-mail has been looking like a GIS chat room as of late.=A0 =
Joe<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=3DMsoAutoSig><font size=3D3 color=3Dnavy face=3D"Times New =
Roman"><span
style=3D'font-size:12.0pt;color:navy'>Joe Noble =
<o:p></o:p></span></font></p>
<p class=3DMsoAutoSig><font size=3D3 color=3Dnavy face=3D"Times New =
Roman"><span
style=3D'font-size:12.0pt;color:navy'>GIS/IS Coordinator =
<o:p></o:p></span></font></p>
<p class=3DMsoAutoSig><font size=3D3 color=3Dnavy face=3D"Times New =
Roman"><span
style=3D'font-size:12.0pt;color:navy'>Tall Timbers Research =
Station<o:p></o:p></span></font></p>
<p class=3DMsoAutoSig><font size=3D3 color=3Dnavy face=3D"Times New =
Roman"><span
style=3D'font-size:12.0pt;color:navy'>850-893-4153=A0 =
x-232<o:p></o:p></span></font></p>
</div>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><font =
size=3D3
face=3D"Times New Roman"><span style=3D'font-size:12.0pt'>
<hr size=3D2 width=3D"100%" align=3Dcenter tabindex=3D-1>
</span></font></div>
<p class=3DMsoNormal><b><font size=3D2 face=3DTahoma><span =
style=3D'font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font =
size=3D2
face=3DTahoma><span style=3D'font-size:10.0pt;font-family:Tahoma'>
shrug-l-admin@lists.dep.state.fl.us
[mailto:shrug-l-admin@lists.dep.state.fl.us] <b><span =
style=3D'font-weight:bold'>On
Behalf Of </span></b>Sykes, John<br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, September =
30, 2005
12:41 PM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> Geographic Systems =
LLC;
shrug-L@lists.dep.state.fl.us<br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> RE: shrug-l: =
Question du
jour</span></font><o:p></o:p></p>
</div>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D4 color=3Dblue face=3DArial><span =
style=3D'font-size:
13.5pt;font-family:Arial;color:blue'>That's a good website. From =
it I
gather that if I want BOTH the distances and azimuths to my sampling =
locations
from the site center to be the most accurate, the Azimuthal Equidistant
projection is the best solution.</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D4 color=3Dblue face=3DArial><span =
style=3D'font-size:
13.5pt;font-family:Arial;color:blue'>I came up with part of the rest of =
your
solution on my own, however, I'm having trouble rotating it through =
360=B0.</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'> <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D4 color=3Dblue face=3DArial><span =
style=3D'font-size:
13.5pt;font-family:Arial;color:blue'>Another solution I thought of, is =
setting
up the sector lines in an AutoCad file, then importing it into my map =
with a
world file using the center point and the intersection of the first =
radial with
the 10 mile buffer ring as the two points.</span></font><o:p></o:p></p>
<p><b><font size=3D5 face=3D"Monotype Corsiva"><span =
style=3D'font-size:18.0pt;
font-family:"Monotype Corsiva";font-weight:bold'>-- =
John</span></font></b> <o:p></o:p></p>
<div>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'> <o:p></o:p></span></font></p>
</div>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><font =
size=3D3
face=3D"Times New Roman"><span style=3D'font-size:12.0pt'>
<hr size=3D2 width=3D"100%" align=3Dcenter tabIndex=3D-1>
</span></font></div>
<p class=3DMsoNormal style=3D'margin-bottom:12.0pt'><b><font size=3D2 =
face=3DTahoma><span
style=3D'font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</spa=
n></font></b><font
size=3D2 face=3DTahoma><span =
style=3D'font-size:10.0pt;font-family:Tahoma'>
Geographic Systems LLC [mailto:info@geographicsystems.com] <br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, September =
30, 2005
12:19 PM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> Sykes, John<br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> RE: shrug-l: =
Question du
jour</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>Hi =
John,<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>I will try to address the first =
part of
your question (drawing lines out 10 miles at 11.25 degree increments) =
and the
last part (projections). The second part of your question (rhumb =
line
from site point to sampling location) may require more =
research.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>Projections – definitely play =
a part
in spatial accuarcy. My guess is you want a projection that =
preserves
direction and distance. A good place to start is the summary =
tables at
the bottom of the map projection poster, <a
href=3D"http://erg.usgs.gov/isb/pubs/MapProjections/projections.html">htt=
p://erg.usgs.gov/isb/pubs/MapProjections/projections.html</a>.
<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>Drawing lines of specific distance =
and
angle. You can do this manually when you sketch a line. With =
Task
set to Create New Feature and Target your line feature class, click the =
sketch
tool (pencil) and click on the first point of your line. Then =
right click
away from the sketch and select “Direction” (or CTRL-A) =
specify an
angle (0 being horizontal – ie “11.25”) and then right =
click
away from sketch again and select “Length” (or CTRL-L) ie
“2mi” (“mi” for miles). Or you can enter =
both the
first time you right click by selecting “Direction/Length” =
(or
CTRL-G). Check out online help for “Creating segments using =
angles
and lengths”.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div>
<p class=3DMsoNormal><em><i><font size=3D2 color=3Dnavy =
face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial;color:navy'>Miguel =
Garriga</span></font></i></em><font
color=3Dnavy><span style=3D'color:navy'><o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>Geographic Systems, =
LLC</span></font><font
color=3Dnavy><span style=3D'color:navy'><o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'><a =
href=3D"http://www.geographicsystems.com">www.geographicsystems.com</a></=
span></font><font
color=3Dnavy><span style=3D'color:navy'><o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>407-261-0451</span></font><font
color=3Dnavy><span style=3D'color:navy'><o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dnavy face=3DArial><span =
style=3D'font-size:
10.0pt;font-family:Arial;color:navy'>cel =
321-279-6019</span></font><o:p></o:p></p>
</div>
</div>
<div>
<div class=3DMsoNormal align=3Dcenter style=3D'text-align:center'><font =
size=3D3
face=3D"Times New Roman"><span style=3D'font-size:12.0pt'>
<hr size=3D2 width=3D"100%" align=3Dcenter tabIndex=3D-1>
</span></font></div>
<p class=3DMsoNormal><b><font size=3D2 face=3DTahoma><span =
style=3D'font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font =
size=3D2
face=3DTahoma><span style=3D'font-size:10.0pt;font-family:Tahoma'>
shrug-l-admin@lists.dep.state.fl.us
[mailto:shrug-l-admin@lists.dep.state.fl.us] <b><span =
style=3D'font-weight:bold'>On
Behalf Of </span></b>Sykes, John<br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, September =
30, 2005
10:21 AM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> =
shrug-L@lists.dep.state.fl.us<br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> shrug-l: =
Question du jour</span></font><o:p></o:p></p>
</div>
<p class=3DMsoNormal><font size=3D3 face=3D"Times New Roman"><span =
style=3D'font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>Since
we (collectively) solved the question I had yesterday, here's a new one =
(put on
your thinking caps - this one's tougher!).</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>Problem</span></font>
<o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>When
establishing environmental sampling locations around a site, we like to =
ensure
that the various distance buffer rings are evenly covered (e.g., in this
case: "site boundary" to 2 miles, 2 - 5 miles and 5 - 10
miles. This is simple to create and check with the standard =
multiple
buffer tool in ArcToolbox.</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>However,
we also like to check that the 16 compass sectors around the site have =
also
been evenly covered*. These 22-1/2=B0 sectors are centered on N, =
NNE, NE,
ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW, NW and =
NNW.</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>So,
what I would like to do is to create these sectors visually, by drawing =
a line
from the origin (an arbitrary "center" point on the site) out =
to 10
miles starting at 11-1/4=B0 compass heading, then rotate around =
22-1/2=B0 and draw
a line, until the 16 sectors are visually =
defined.</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>Any
suggestions as how this can be done (easily)? Previously, when =
doing this
in AutoCad, I used a radial copy command. I haven't noticed a =
similar
command in ArcGIS.</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>Finally,
once the sampling location is selected (and the lat/long of that =
location
determined), we need to be able to determine and list the distance and =
azimuth
(rhumb line) from that arbitrary "center" point on the site to =
the
sampling location and put it into the sampling location attributes table =
(in
the past, I've done this using the NGS "Inverse" program =
[fudging the
rhumb line from the great circle azimuths] using a batch file =
input/output) for
atmospheric dispersion modeling. However, I don't see any easy way =
to do
this with ArcInfo (especially on a batch file basis). Any =
suggestions?</span></font><o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>Finally,
food for thought -- How does the projection being used effect the =
accuracy of
all of this? Normally we use Albers (equal area) or Mercator =
(which gives
the most accurate rhumb lines), but is there a better projection to use =
to
obtain accurate distances & azimuths? I understand from the =
reading
I've done that these functions may be rather =
projection-sensitive.</span></font><o:p></o:p></p>
<p><b><font size=3D5 face=3D"Monotype Corsiva"><span =
style=3D'font-size:18.0pt;
font-family:"Monotype Corsiva";font-weight:bold'>-- =
John</span></font></b> <o:p></o:p></p>
<p><font size=3D4 face=3DArial><span =
style=3D'font-size:13.5pt;font-family:Arial'>*Sometimes
if there is a prevailing wind bias, we'll bias our sampling locations to =
that
prevailing wind direction, but in the current case there is no strong
prevailing wind direction - the annual wind rose shows an almost random
360=B0pattern.</span></font><o:p></o:p></p>
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