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SOCNET  March 2011

SOCNET March 2011

Subject:

Re: Geospatial Tutorial Datums and Projections RE: [SOCNET] Geograpical Coordinates in NetDraw - please help!

From:

Manish Nag <[log in to unmask]>

Reply-To:

[log in to unmask]

Date:

Tue, 8 Mar 2011 13:24:23 -0700

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (381 lines)

*****  To join INSNA, visit http://www.insna.org  *****

For those who don't want to install Google Earth, there are some options:

Here is a nice mashup with Google Maps that allows one to click on a
location and get the latitude and longitude values.

http://www.gorissen.info/Pierre/maps/googleMapLocationv3.php

If one wants to find coordinates based on an address, one can look up the
address in Google Maps and then press the "Link" link above the map image.
  In the "email link" textbox that appears, the lat and lon values follow
after "sll=" in the link text. Here is a link when I search for the Empire
State Building in New York.

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=Empire+State+Building,+New+York,+NY&aq=2&sll=40.287016,-74.547795&sspn=0.00807,0.018346&ie=UTF8&hq=&hnear=Lifespire+Inc+Empire+State+Bldg,+350+5th+Ave,+New+York+10001&t=h&z=14

Best,
Manish


> *****  To join INSNA, visit http://www.insna.org  *****
>
>
> ehm...on a much easier level, how do I actually get latitude and longitude
> values? I have data on links between Italian universities, and it would be
> great to project the network on a map.sorry for stepping back the
> conversation on a more trivial matter
> elisa
>
>> Date: Mon, 7 Mar 2011 14:51:52 -0700
>> From: [log in to unmask]
>> Subject: Re: Geospatial Tutorial Datums and Projections RE: [SOCNET]
>> Geograpical Coordinates in NetDraw - please help!
>> To: [log in to unmask]
>>
>> *****  To join INSNA, visit http://www.insna.org  *****
>>
>> One note about Sonoma: it uses the GMT package for rendering maps and
>> ties. This means that you can render your graphs without worrying about
>> translating spherical coordinates to x,y coordinates. You can submit the
>> coordinates of your actors via any number of latitude and longitude
>> formats (decimal or degree:minute:seconds, postiive/engative values, or
>> East/West coords).
>>
>> -Manish
>>
>> > There could also be a projection/datum issue or negative coordinates,
>> > which become important as you try to overlay different datasets.  This
>> is
>> > the main reason why novice GIS users can’t get maps/coordinates to
>> line
>> > up.  Even if this isn’t the current problem you have, if you ever
>> want
>> > to match up your geospatial data with other maps, you’ll need to
>> know
>> > the basics. Here is some info I pulled from the ESRI (ArcGIS) site.
>> They
>> > have excellent help files that explain these concepts--it’s all
>> about
>> > datums, geographic systems, projected coordinates, and negative lat
>> > /longs! You need to know the datum of your coordinates and of any
>> system
>> > that you want to project your coordinates into otherwise your points
>> may
>> > not project.
>> >
>> > A datum defines the position of the spheroid (approximation of the
>> earth)
>> > relative to the center of the earth.  A datum provides a frame of
>> > reference for measuring locations on the surface of the earth. It
>> defines
>> > the origin and orientation of the latitude and longitude lines. So
>> datum
>> > tells you where the x,y of your lat/longs begin.
>> > http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//003r00000008000000.htm
>> >
>> > Today we are moving towards a universal datum WGS 1984, but there are
>> > numerous datums out there.  In the link above you can see what happens
>> if
>> > you try to overlay points in different datums (sometimes the error is
>> OK
>> > and sometimes the error is not OK). People know enough to collect
>> lat/long
>> > points nowadays but they don’t understand that you need the datum as
>> > well. I mapped out the official fisheries management areas in Chile to
>> > find out that half of the management area located on the land if you
>> used
>> > the official coordinates! To get an idea of how many datums and
>> geographic
>> > coordinate systems are out there, you can see the attached file
>> > http://help.arcgis.com/en/arcgisdesktop/10.0/help/003r/pdf/geographic_coordinate_systems.pdf
>> >  What do you do if you have lat longs and no idea what the coordinate
>> > system is? First try WGS 84. If that doesn’t work, then you could
>> guess
>> > based on what people tend to use locally. In Brazil people use PSAD
>> 1956.
>> > In Chile, people use SAD 1969. In North America people use NAD 1927.
>> Maps
>> > should also have the datum and projection written on them, though most
>> > don’t. Many cases there is metadata that has the datum/projection
>> info.
>> > This is true of satellite images that you may download or other
>> > geospatially explicit datasets.
>> >
>> > A geographic coordinate system is a three-dimensional spherical
>> surface to
>> > define locations of the earth (which is often confused with a datum).
>> A
>> > GCS contains the angular unit of measure, a prime meridian, and a
>> datum
>> > (based on a spheroid)
>> > http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_are_geographic_coordinate_systems/003r00000006000000/
>> >
>> > Finally you have projected coordinate system, which is a flat 2-D
>> surface.
>> >  Unlike a geographic coordinate system, a projected coordinate system
>> has
>> > constant lengths, angles, and areas across the two dimensions. A
>> projected
>> > coordinate system is always based on a geographic coordinate system
>> that
>> > is based on a sphere or spheroid.
>> > http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_are_projected_coordinate_systems/003r0000000p000000/
>> > Certain projection systems have particular datums associated with
>> them. So
>> > if you try to put lat long into a projected coordinate system, you
>> need to
>> > know the datums of both and transform the data so they are in equal
>> > systems.  There are many projected coordinate systems out there. To
>> get an
>> > idea of how many see here.
>> > http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//003r00000017000000.htm
>> >
>> > Finally, if you are working in a place where you have a negative
>> latitude
>> > or longitude, you may have positive numbers written down instead of
>> > negative numbers. Locally people say or even write down  the positive
>> > number, even though the number is really negative. So you need to
>> check if
>> > you are working in a negative zone because this could also be a source
>> of
>> > error.
>> >
>> > I hope this basic geospatial tutorial helps!
>> >
>> > Tracy Van Holt
>> > Assistant Professor
>> > East Carolina University
>> > [log in to unmask]<mailto:[log in to unmask]>
>> >
>> >
>> >
>> > From: Social Networks Discussion Forum [mailto:[log in to unmask]]
>> On
>> > Behalf Of [log in to unmask]
>> > Sent: Monday, March 07, 2011 1:18 PM
>> > To: [log in to unmask]
>> > Subject: Re: [SOCNET] Geograpical Coordinates in NetDraw - please
>> help!
>> >
>> > I can also recommend the Sonoma package that I presented at Sunbelt
>> this
>> > year. The package allows for geographic visualization of network data,
>> > with fine tuned control of tie width and tie coloring, in addition to
>> > integration with GIS packages like ArcGIS.
>> >
>> > http://www.princeton.edu/~mnag/sonoma/
>> >
>> > Best,
>> >
>> > Manish Nag
>> > Doctoral Candidate, Sociology
>> > Princeton University
>> > ----- Reply message -----
>> > From: "Jamie Olson" <[log in to unmask]>
>> > Date: Thu, Mar 3, 2011 10:33 am
>> > Subject: [SOCNET] Geograpical Coordinates in NetDraw - please help!
>> > To: <[log in to unmask]>
>> > ***** To join INSNA, visit http://www.insna.org *****
>> > Hi Stephanie,
>> > I just want to add that ORA provides a bit more than just layout with
>> > lat/lon.  There are also a variety of exploratory analysis features,
>> > including spatial clustering w/feedback and sizing/coloring by network
>> > structure statistics.  ORA also contains extensions of several
>> standard
>> > network centrality measures that take into account the spatial
>> > information.
>> >
>> > I think it's great that people have brought up visualization in Google
>> > Earth.  ORA also allows export to KML, but I thought I'd mention a
>> problem
>> > I've come across.  Google Earth may not provide a truthful rendering
>> of
>> > lines at various levels of resolution.  They have a complicated
>> caching
>> > process that often results in a sort of flickering as you zoom in and
>> out,
>> > which I've found distracting.
>> >
>> > I saw that Dr. Owens recommended MapWindow.  I don't have much
>> experience
>> > with MapWindow, which seems to be a fine product, but I noticed that
>> it is
>> > not a cross-platform tool.  If you need to or would like to work on
>> > non-windows systems, there are a number of other open source GIS
>> tools.
>> > I've had about the most success with
>> OpenJUMP<http://www.openjump.org/>,
>> > but qgis<http://www.qgis.org/> is also easy to use.
>> >
>> > Good luck,
>> > --Jamie
>> >
>> > Jamie Olson
>> > School of Computer Science
>> > Carnegie Mellon University
>> > 5000 Forbes Ave.
>> > Pittsburgh, PA 15213
>> > [log in to unmask]<mailto:[log in to unmask]>
>> >
>> > On Thu, Mar 3, 2011 at 4:13 AM, Clement Levallois
>> > <[log in to unmask]<mailto:[log in to unmask]>> wrote:
>> > ***** To join INSNA, visit http://www.insna.org *****
>> >
>> > Hi Stephanie,
>> >
>> > If you are still stuck with your geo layout, you can try:
>> >
>> > - Gephi, which has a layout plugin for this purpose:
>> > http://gephi.org/tag/geolayout/
>> >
>> > - ORA also provides a layout of long / lat coordinates I believe
>> > http://www.casos.cs.cmu.edu/projects/ora/
>> >
>> > Good luck!
>> >
>> > Clement
>> >
>> > ___________________
>> > Clement Levallois, PhD
>> > Erasmus University
>> > The Netherlands
>> > [log in to unmask]<mailto:[log in to unmask]> |
>> > www.clementlevallois.net<http://www.clementlevallois.net> | Twitter:
>> > @seinecle
>> >
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: Social Networks Discussion Forum on behalf of Eric DesMarais
>> > Sent: Wed 02/03/2011 22:37
>> > To: [log in to unmask]<mailto:[log in to unmask]>
>> > Subject: Re: [SOCNET] Geograpical Coordinates in NetDraw - please
>> help!
>> >
>> > *****  To join INSNA, visit http://www.insna.org  *****
>> >
>> > Since you have coordinate data, it sounds like the easiest thing to do
>> > would
>> > be to use GIS software such as ArcGIS, use your network visual as an
>> > overlay, and stretch it to fit over the map, matching the coordinate
>> data
>> > of
>> > your nodes to the coordinate data of the map.
>> >
>> > It is exciting to see another doctoral student in social work using
>> maps
>> > and
>> > networks.  Hope your project goes well.
>> >
>> > --
>> > Eric DesMarais, MSW, LCSW
>> > Doctoral Student
>> > Graduate School of Social Work
>> > University of Denver
>> > 2148 South High Street
>> > Denver, CO 80208
>> > 720-413-5809
>> >
>> > On Wed, Mar 2, 2011 at 8:29 AM, Stephanie Smith <
>> > [log in to unmask]<mailto:[log in to unmask]>>
>> wrote:
>> >
>> >> ***** To join INSNA, visit http://www.insna.org *****
>> >> I have been trying to figure out how to project the image of my
>> network
>> >> on
>> >> to a map and have not been successful. I have the latitude and
>> longitude
>> >> of
>> >> each node and have made them into attribute files so to place the
>> nodes
>> >> with
>> >> their location on the map. However, once I'm in NetDraw and click on
>> >> Layout/Coordinates as Attrbutes and try to complete the steps, my
>> >> network
>> >> vanishes! **Poof**
>> >>
>> >> Has this ever happened to anyone else? If so, do you know what I am
>> >> doing
>> >> wrong?
>> >>
>> >> Any help you could lend would be greatly appreciated.
>> >>
>> >> Thank you!
>> >>
>> >> Stephanie Smith
>> >> PhD Student
>> >> School of Sociology, Social Policy & Social Work
>> >> Queen's University Belfast
>> >>  6 College Park
>> >> Belfast BT7 1LP
>> >> Northern Ireland
>> >>
>> >>
>> >>
>> >>  _____________________________________________________________________
>> >> SOCNET is a service of INSNA, the professional association for social
>> >> network researchers (http://www.insna.org). To unsubscribe, send an
>> >> email
>> >> message to [log in to unmask]<mailto:[log in to unmask]>
>> >> containing the line UNSUBSCRIBE SOCNET
>> >> in the body of the message.
>> >
>> > _____________________________________________________________________
>> > SOCNET is a service of INSNA, the professional association for social
>> > network researchers (http://www.insna.org). To unsubscribe, send
>> > an email message to
>> [log in to unmask]<mailto:[log in to unmask]>
>> > containing the line
>> > UNSUBSCRIBE SOCNET in the body of the message.
>> >
>> >
>> > ________________________________
>> > Disclaimer
>> > De informatie verzonden in dit e-mail bericht inclusief de bijlage(n)
>> is
>> > vertrouwelijk en is uitsluitend bestemd voor de geadresseerde van dit
>> > bericht. Lees verder: http://www.eur.nl/email-disclaimer.
>> >
>> > The information in this e-mail message is confidential and may be
>> legally
>> > privileged. Read more: http://www.eur.nl/english/email-disclaimer.
>> > ________________________________
>> >
>> > _____________________________________________________________________
>> > SOCNET is a service of INSNA, the professional association for social
>> > network researchers (http://www.insna.org). To unsubscribe, send an
>> email
>> > message to [log in to unmask]<mailto:[log in to unmask]>
>> > containing the line UNSUBSCRIBE SOCNET in the body of the message.
>> >
>> > _____________________________________________________________________
>> > SOCNET is a service of INSNA, the professional association for social
>> > network researchers (http://www.insna.org). To unsubscribe, send an
>> email
>> > message to [log in to unmask] containing the line UNSUBSCRIBE
>> SOCNET
>> > in the body of the message.
>> >
>>
>> _____________________________________________________________________
>> SOCNET is a service of INSNA, the professional association for social
>> network researchers (http://www.insna.org). To unsubscribe, send
>> an email message to [log in to unmask] containing the line
>> UNSUBSCRIBE SOCNET in the body of the message.
>
> _____________________________________________________________________
> SOCNET is a service of INSNA, the professional association for social
> network researchers (http://www.insna.org). To unsubscribe, send
> an email message to [log in to unmask] containing the line
> UNSUBSCRIBE SOCNET in the body of the message.
>

_____________________________________________________________________
SOCNET is a service of INSNA, the professional association for social
network researchers (http://www.insna.org). To unsubscribe, send
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