From healthmaps@attbi.com Mon Dec 2 10:05:43 2002 Received: from mailscan4.cac.washington.edu (mailscan4.cac.washington.edu [140.142.33.15]) by lists.u.washington.edu (8.12.1+UW01.12/8.12.1+UW02.11) with SMTP id gB2I5hrw019486 for ; Mon, 2 Dec 2002 10:05:43 -0800 Received: FROM mxu1.u.washington.edu BY mailscan4.cac.washington.edu ; Mon Dec 02 10:05:42 2002 -0800 Received: from sccrmhc02.attbi.com (sccrmhc02.attbi.com [204.127.202.62]) by mxu1.u.washington.edu (8.12.1+UW01.12/8.12.1+UW02.11) with ESMTP id gB2I5g8I020542 for ; Mon, 2 Dec 2002 10:05:42 -0800 Received: from harriet (12-229-18-75.client.attbi.com[12.229.18.75]) by sccrmhc02.attbi.com (sccrmhc02) with SMTP id <2002120218054000200soi1ce>; Mon, 2 Dec 2002 18:05:41 +0000 From: "HealthMaps" To: Subject: RE: WAPHGIS: long/lat precision Date: Mon, 2 Dec 2002 10:05:43 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0031_01C299EA.601374C0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) In-Reply-To: <27C204BD76CBC142BA1AE46D62A8548E02F08BC4@nihexchange9.nih.gov> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0031_01C299EA.601374C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit This is one of those "I should have thought of that ..." thanks! We have a real geographer here... In summary, (sorry to bore most of you with "feet" and "miles" , I think Americans are the last to use these.) 10,000,000 meters /90 degrees = 111111.1111 meters/degree latitude 111.11 kilometers/degree 69.0412 miles/degree So for my location 47 degrees lat at -123 long Latitude (same everywhere) ..1 is 11,111.1 meters 6.904 miles ..01 is 1,111 or 3645.0131 feet ..001 is 111.1 364.5013 ..0001 is 11.11 36.4501 ..00001 is 1.111 3.6450 Longitude (at 47 degrees) 1 is 11,111.1 meters 6.904 miles x cos(47 degrees)= 7577.75 meters or 4.7085 miles ..01 is 1,111 or 3645.0131 feet x cos(47 degrees)= 757.775 or 2486.13 feet ..001 is 111.1 364.5013 x cos(47 degrees)= 75.77 248.6 ..0001 is 11.11 36.4501 x cos(47 degrees)= 7.57 24.8 ..00001 is 1.111 3.6450 x cos(47 degrees)= .76 2.5 hopefully I have done this right. for a nice online calculator/converter see: http://www.convertit.com/Go/ConvertIt/ or http://www.1728.com/ The motivation for this exercise is that I get geocoded data out to .00001 degrees or stated precision of ~ .8 meters. Essentially a random number. For geocoding using TIGER or parcels likely somewhere between .001 and .0001 is the best that can be stated. My GPS is good to 17 feet when all the satellites can be seen, or 5.2 meters. Richard E Hoskins PhD MPH Spatial Epidemiology Unit WA State Dept of Health 1102 Quince Street Olympia, WA 98504-7812 richard.hoskins@doh.wa.gov GMT -8 to join WAPHGIS: send email to listproc@u.washington.edu with the following request: subscribe WAPHGIS Your Name new on-line GIS, geography & health journal: http://www.ij-healthgeographics.com/start.asp -----Original Message----- From: WAPHGIS-owner@u.washington.edu [mailto:WAPHGIS-owner@u.washington.edu]On Behalf Of Boscoe, Francis (NIH/NCI) Sent: Monday, December 02, 2002 5:58 AM To: 'waphgis@u.washington.edu' Subject: RE: WAPHGIS: long/lat precision I always use 10 million meters = 90 degrees latitude. This was how the meter was originally defined when the metric system was invented in the 1790s. For longitude, the same relation holds, except that you have to multiply the result by the cosine of the latitude. Thus, 0.01 degrees latitude corresponds to 1,111 meters, and 0.01 degrees longitude at 45 degrees latitude corresponds to 786 meters. This, of course, assumes the earth is a sphere, but the result is accurate to about 4 significant figures. Francis P. Boscoe, Ph.D. Health Statistician and Geographer SEER Program National Cancer Institute 6116 Executive Blvd Room 5007 Bethesda, MD 20892 -----Original Message----- From: HealthMaps [mailto:healthmaps@attbi.com] Sent: Sunday, December 01, 2002 7:47 AM To: Maptitude; WAPHGIS Subject: WAPHGIS: long/lat precision Does anyone have a table (or formula) that gives the distance on the ground for various levels of precision of longitude and latitude? For example: for a specified latitude, what is the distance on the ground for .1 degrees, .01 degrees, .001 degrees, .... .000001 degrees? For a latitude y, and a specified longitude, what is the distance on the ground for .1 degrees, .01 degrees, .001 degrees, .... .000001 degrees? Thanks, Richard E Hoskins PhD MPH Spatial Epidemiology Unit WA State Dept of Health 1102 Quince Street Olympia, WA 98504-7812 richard.hoskins@doh.wa.gov GMT -8 to join WAPHGIS: send email to listproc@u.washington.edu with the following request: subscribe WAPHGIS Your Name new on-line GIS, geography & health journal: http://www.ij-healthgeographics.com/start.asp ------=_NextPart_000_0031_01C299EA.601374C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
This is one of those "I should have thought of that ..."  = thanks! We=20 have a real geographer here...
 
In summary, (sorry to bore most of you with "feet" and = "miles" , I=20 think Americans are the last to use these.) =
 
10,000,000 meters /90 degrees =3D 111111.1111 meters/degree=20 latitude
          &nbs= p;            = ;        =20 111.11 kilometers/degree
          &nbs= p;            = ;          69.0412=20 miles/degree  
 
 
So for my location  47 degrees lat at -123=20 long
 
Latitude (same everywhere)
.1  is 11,111.1 meters     6.904 miles =
.01 is 1,111         =20 or   3645.0131 feet
.001 is=20 111.1           &n= bsp;  =20 364.5013
.0001 is=20 11.11           &n= bsp;   36.4501
.00001 is=20 1.111           &n= bsp;  =20 3.6450
 
Longitude (at 47 degrees)
 
1  is 11,111.1 meters     = 6.904=20 miles     x cos(47 degrees)=3D 7577.75 meters or = 4.7085=20 miles
.01 is 1,111         =20 or   3645.0131 feet x cos(47 degrees)=3D =20 757.775  or  2486.13=20 feet          =
.001 is=20 111.1           &n= bsp;  =20 364.5013      x cos(47 = degrees)=3D  =20 75.77        = 248.6
.0001 is=20 11.11           &n= bsp;   36.4501     =20 x cos(47 degrees)=3D   =20 7.57         = 24.8
.00001 is=20 1.111           &n= bsp;  =20 3.6450      x cos(47 = degrees)=3D   =20 ..76           2.5 =
 
hopefully I have done this right.
 
for a nice online calculator/converter see: = http://www.convertit.com/Go/ConvertIt/
or   = http://www.1728.com/=20
 
The = motivation for=20 this exercise is that I get geocoded data out to .00001 degrees or = stated=20 precision of  ~ .8 meters. Essentially a random number. For = geocoding=20 using TIGER or parcels likely somewhere between .001 and .0001 is the = best=20 that can be stated. My GPS is good to 17 feet when all the satellites = can be=20 seen, or 5.2 meters.
Richard E Hoskins PhD = MPH
Spatial=20 Epidemiology Unit
WA State Dept of Health
1102 Quince = Street
Olympia,=20 WA 98504-7812
richard.hoskins@doh.wa.gov
GMT -8
to join=20 WAPHGIS: send  email to listproc@u.washington.edu
with the following = request:

subscribe WAPHGIS = Your Name 

new on-line=20 GIS, geography & health journal:
http://www.ij-healthgeographics.com/start.asp<= /SPAN>


 
=
 
 

 
 -----Original=20 Message-----
From: WAPHGIS-owner@u.washington.edu=20 [mailto:WAPHGIS-owner@u.washington.edu]On Behalf Of Boscoe, = Francis=20 (NIH/NCI)
Sent: Monday, December 02, 2002 5:58 = AM
To:=20 'waphgis@u.washington.edu'
Subject: RE: WAPHGIS: long/lat = precision=20

I always use 10 million meters =3D 90 = degrees latitude.=20 This was how the meter was originally defined when the metric system = was=20 invented in the 1790s.
 
For longitude, the same relation holds, = except that=20 you have to multiply the result by the cosine of the=20 latitude.
 
Thus, 0.01 degrees latitude corresponds to = 1,111=20 meters, and 0.01 degrees longitude at 45 degrees latitude corresponds = to 786=20 meters.
 
This, of course, assumes the earth is a = sphere, but=20 the result is accurate to about 4 significant = figures.

Francis P. Boscoe, = Ph.D.=20
Health Statistician and Geographer
SEER Program
National Cancer = Institute=20
6116 Executive Blvd
Room = 5007=20
Bethesda, MD 20892 =


-----Original Message-----
From: = HealthMaps=20 [mailto:healthmaps@attbi.com]
Sent: Sunday, December 01, = 2002 7:47=20 AM
To: Maptitude; WAPHGIS
Subject: WAPHGIS: = long/lat=20 precision

Does=20 anyone have a table (or formula) that gives the distance on the = ground for=20 various levels of precision of longitude and = latitude?
 
For=20 example:  for a specified latitude,  what is the = distance on=20 the ground for .1 degrees, .01 degrees, .001 degrees, .... .000001 = degrees?=20  
 
For a=20 latitude y, and a specified longitude, what is the distance on the = ground=20 for .1 degrees, .01 degrees, .001 degrees, .... .000001=20 degrees?  
 
Thanks,=20
 
Richard E Hoskins PhD = MPH
Spatial=20 Epidemiology Unit
WA State Dept of Health
1102 Quince=20 Street
Olympia, WA 98504-7812
richard.hoskins@doh.wa.gov
GMT -8
to join WAPHGIS: send  email to listproc@u.washington.edu
with the following=20 request:

subscribe WAPHGIS Your Name 

new on-line = GIS, geography=20 & health journal:
http://www.ij-healthgeographics.com/start.asp<= /SPAN>
------=_NextPart_000_0031_01C299EA.601374C0-- .