Ask MetaFilter questions tagged with coordinates

Help me understand homogenous coordinates

tickingclock — Thu, 22 Oct 2009 19:37:11 -0800

Help me understand homogenous coordinates! I encountered homogenous coordinates in computer graphics, where I understand that they let us translate vertices. But this is a rather shallow level of understanding, and I don't really get why, for instance, the position of the light source in OpenGL is necessarily specified with (x, y, z, w). Is it kind of like how there is an infinite number of points that can correspond to a single point on a 2D image at (x, y), but by specifying a third dimension, we can disambiguate between the different points?

I've tried reading Googling and I've tried reading Wikipedia -- but to no avail. I'm really hoping that somebody in the hive mind can explain it at a level that I can understand, and also why homogenous coordinates are important on a more broad level. Thanks!

Longitude Latitude Database

AdamOddo — Wed, 29 Jul 2009 10:26:49 -0800

A few years ago I had bookmarked a website that had a very plain search feature that allowed you to search names of all sorts of geographical whathaveyou and gave a table complete with longitude and latitude coordinates. I believe this site was US-centric (might have been USGS but I looked and failed) although it was possible to search for anything, world-wide. Ring any bells?

NYC subway station coordinates?

lupefiasco — Thu, 21 May 2009 11:10:40 -0800

Where can I find a listing of the coordinates (latitude, longitude) of all the New York City subway stations?

paint by numbers and then number by painting

ian1977 — Wed, 11 Mar 2009 16:30:58 -0800

How can I convert a list of x, y, R, G, B coordinates into a bitmap? My previous question asked if there was a way to convert a bitmap into a usable set of x, y, z coordinates. A dead simple solution using the program ImageJ was suggested by kisch mokusch.

But now I need to know how to do this backwards. Meaning, how can I convert a set of [x, y, R, G, B] coordinates back into a bitmap?

Ideally the solution will not involve coding. Is there is an existing solution for this type of thing?

Cartesian bitmap?

ian1977 — Tue, 03 Mar 2009 18:40:29 -0800

Is there a convenient way to convert image files into x, y, z coordinates I'd like to be able to take a greyscale image and convert each pixel into an x, y, z coordinate. The z would be the greyscale of each pixel. Is doesn't matter if the scaling is off, relative numbers are fine and can be converted later.

Is there a way I can do this?

Original file type doesn't matter too much to me, but most convenient would be bitmaps.

Grid Mapping in the USA

Xurando — Sat, 10 Jan 2009 14:11:22 -0800

Help me find or create a grid with GPS coordinates of every square mile of the USA. Can I use Expert GPS or Google Earth to do this? Has this been done before by government or other entities (Google Maps, etc.) What are some problems in creating such a grid? Can I use Expert GPS to do this?

Where in the world am I?

mcarthey — Sat, 12 Apr 2008 19:14:02 -0800

Can I find coordinates by address? I would like to know if it's possible to locate a set of GPS coordinates by typing in an address? Specifically I am looking for international addresses (South America). The maps that I have been able to find online are not specific enough for South America to allow me to use them.
Thanks for any help!

Help Align my fuzzy images

bleucube — Fri, 01 Feb 2008 04:54:11 -0800

How do I get my images where I want? I'm trying to overlay images on a background. Is there a fancy tool I could use that will tell me the exact coordinates? Should I not try tables and do some fancy css? Or am I going at this ass backwards? Here's what I'm talking about. It's a self link, but nothing really to see but my issue. View the source to see my attempt.

molecular dynamics animator

SBMike — Fri, 25 May 2007 12:31:18 -0800

Help me find software to animate my molecular dynamics simulation For my research, I've been trying to learn about molecular dynamics simulations. I've been trying to learn by writing up a simple MD algorithm from scratch in Java. I only have a limited knowledge of computer programming, so my simulation is probably far from the most elegant, efficient, or functional program. Nevertheless, I have managed to write a program that calculates the forces, trajectories, and velocities for a group of N particles. The program also exports the simulation output into a .txt file. There is no graphical interface, and I don't really want to program one.

I'm looking for some software that will do the animation for me. The form of the output is a list (N long) of x and y coordinates. There are as many of these lists as there are time steps in the simulation. So, for example, for 10 particles with 20 time steps, the output file would be 20 10x2 arrays. This output can be formatted or modified slightly. I'm looking for a simple program that will read those coordinates from the output file and animate them with respect to time. Free and easy to use are what I'm looking for.

Why is China blocking my diplomacy?

disgustipated — Mon, 09 Oct 2006 12:47:33 -0800

Why is it that if I enter the coordinates of Tiananmen Square (which are 39°54′12″N, 116°23′30″E) in any format, Google Earth responds with "Your search returned no results"? I have tried entering the coordinates in several formats. Am I being blocked? Beijing's coordinates (Latitude: 39° 55' 44 N, Longitude: 116° 23' 18 E) work.

Thanks!

Land Survey coordinates to UTM

orlin — Tue, 14 Feb 2006 11:34:06 -0800

Is anyone aware of a program that converts The United States Public Land Survey (such as found on platt maps) coordinates into UTM coordinates? I would like to input land survey coordinates and have it convert the data to UTM coordinates for my GPS. Many thanks...

I need a map on which I can plot lat. and lon. coordinates

pantufla — Thu, 27 Oct 2005 21:56:10 -0800

Hi all, I am looking for an website that will let me enter in Latitude and Longitude coordinates from various countries and plot them on a map interactively. Failing that, I'd like a map that I can print out and plot coordinates on with rough accuracy. Thanks!

Where to get postcodes and map them to distances?

reklaw — Tue, 15 Mar 2005 05:16:55 -0800

I'd like to store people's postcodes and work out distances between them. I think I need a postcode-to-coordinates database, and then a way of working out the distances... So, two questions really:

1. Where can I get a database mapping postcodes to latitude and longitude (or some other better co-ordinate system)? Free is the best price, but not essential, and the UK is the most important place to cover, but as many as possible would be nice.
2. Once I had such a thing, how would I go about working out the distances between postcodes with it?

PS. This is for a free project, not a business or my job or anything.

Maps and Coordinates

dodgygeezer — Fri, 26 Nov 2004 06:49:59 -0800

Maps and coordinates. I'm testing out the feasibility of using maps on my website. The website providing the maps asks for particular types of coordinates yet I can't seem to find a way of working out what my coordinates should be. This could be complicated to explain so... [more inside] So I want to use Map24.com to map my users coordinates and to show their nearest neighbours

In the docs they give this example of usable coordinates:
Location in World coordinates (stated in minutes).
Example Mapsolute HQ in Eschborn:
wx=514.227597291174&wy= 3007.8407347798347

So my plan is that if my users can get their coordinates from somewhere then they can just enter X and Y into their profile and we're laughing.

The problem is I can't work out where they can get these coordinates from. For example if I find an address on Multimap it gives me the following coordinates:
X: 530400m
Y: 184800m
Lat: 51:32:49N (51.5471)
Lon: 0:07:13W (-0.1202)

Which is great, except it seems to bear no relation to what Map24 wants and any version of those numbers that I put in ends up going straight into the sea. Splash.

So my questions are:
Can I easily convert those coordinates?
Can I find a better source for providing my users with coordinates that'll be Map24 compatible?
Is there a better all round solution somewhere else?