***** 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
> >>
> >>
> >>
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