 Vector data- making polygons, outlines, like coastline

 Raster data, 2D arrays, gridded data  Color, or rainfall, or elevation

 2d data  Computer stores data as bits (ones and zeros)  1-bit array Ex: (1=white, 0=black)  More complex data: eight bits=byte  1 byte=2 8 =256 possibilities => gray scale with 256 intensities of black to white, or 256 values of a colorscale (use colormaps)  Still not good enough for good maps…  24-bit system; 8 bits for each RGB channel=256 3 =16,777,216 colors  24 bit storage requires lots of memory!!!

 Compuserve Graphics Interchange Format (GIF):  256 colors, Compression without data loss-Designed for fast transfer over the internet, Good for line art, simple maps, cartoons, logos  Microsoft Windows Bitmap Format (BMP)  Native bitmap format for Windows OS, Converters exist to read and write BMP files on other platforms  Tagged Image File Format (TIFF)  Includes an image file header, a drectory, and the data in all available graphics and image file formats; Vector and raster versions; Designed to be very portable- any computer platform BUT, evolution caused incompatibilites…Thousands of Incompatible File Formats  PICT  Apple; Rasters and vectors; PICT not supported by other platforms

 PostScript (PS) Encapsulated PostScript (EPS)  Xerox/ Aldus (Adobe)/Apple; Vector format  PS-generally single-page format, illustration of a text  EPS- included in other pages, contain combination of text, graphics, and images  Joint Photographic Experts Group (JPEG)  Image compression and format; Irreversible compression (data lost); Three channel- 24 bit true color  Portable Document Format (PDF)  Adobe; Cross-platform; Contains complete formatting of vector illustrations, raster images, and text; Highly compressed; Fast internet download

  Make new directory in your matlab space  Download and save image

 On command line ….( pg 231)  Picture1=imread(‘ name of image.jpg’);  imshow (Picture1);  PictureGray=rgb2gray (Picture1);  imshow (Picture1), figure, imshow(PictureGray);  Follow remaining instruction on pg  NOTE there is a TYPO in Book: iminfo (‘PictureGray.jpg’);  To hand in: the 3 images (rgb, grayscale, and indexed rgb)

 Raster data: Digital Elevation maps  ETOPO1: 1 arc minute resolution  GTOPO30: 30 arc seconds (~1 km) resolution  Shuttle Radar Topography Mission (SRTM) 30, 90 m res.

 Raster data: ETOPO1   Custom grids- ngdc  Your grid ID: you pick a name, like mygrid01  Grid databas: ETOPO1  Latitude 30 E 60E Longitude 20N 20 S  Grid Cell size 1 min  Grid Format ASCII raster  SUBMIT  w/software, w/ geography, w/coastline  Compress and retrieve  …wait while it processes….  Retrieve  …wait while it downloads….  Save your data in a folder that matlab sees  decompress (unzip)

 Let’s look at the data and header info  On command line of terminal window type  !head MyGrid01.asc (or whateer the name of your data)  You are now viewing the first few lines of the data that you imported  You want to plot the data, so you have to remove the header info from your data file: NewMyGrid=dlmread(‘MyGrid.asc’,’’,6,0);  Now save your new data file save newMyGrid.mat NewMyGrid  Now follow the directions from page  With the same data, modify script on page 172