SAFARI 2000 Hydrographic Data, 1-Deg, Release 2.2 (Cogley) ------------------------------------------------------------------- Abstract -------- The Global Hydrographic data set (GGHYDRO) Release 2.2 is a data set containing hydrographic data on the areal extent of different kinds of terrain, and on the distribution of mean terrestrial surface run-off. It is organized into 19 files containing terrain type, stream frequency counts, major drainage basins, main features of the cryosphere surface, and ice/water runoff per year for the entire Earth's surface at a spatial resolution of 1 degree longitude by 1 degree latitude. Complete information on the Global Hydrographic data set is available as downloadable documents from the anonymous ftp site at Trent Univeristy: ftp://ftp.trentu.ca/pub/gghydro/. ========================================================================= Background Information ---------------------- Investigators: J. Graham Cogley gcogley@trentu.ca Project: SAFARI 2000 Data Set Title: SAFARI 2000 Hydrographic Data, 1-Deg, Release 2.2 (Cogley) Site: Southern Africa Westernmost Longitude: 5 Easternmost Longitude: 60 Northernmost Latitude: 5 Southernmost Latitude: -35 Temporal Resolution: Annual average Data Set Citation: Cogley, J. G. 2002. SAFARI 2000 Hydrographic Data, 1-Deg, Release 2.2 (Cogley). Available on-line [http:/www.daac.ornl.gov] from the Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. Southern African subset extractions of this data were performed by Oak Ridge National Laboratory: ORNL DAAC User Services Office ornldaac@ornl.gov +1 (423) 241-3952 Original Data Set Link: ftp://ftp.trentu.ca/pub/gghydro/ ========================================================================= Data File Information --------------------- This data set consists of 19 separate ASCII data files, each one with an accompanying binary image file: 1.gghbas1.dat* --> Major drainage basins, ~30 drainage systems 2.gghbas2.dat* --> Smaller drainage basins, ~150 drainage systems 3.gghcryo.dat* --> Main features of the cryosphere 4.gghdsrf.dat --> Dry surface (% of grid cell) 5.gghdune.dat** --> Sand dunes (% of grid cell) 6.gghflak.dat** --> Perennial freshwater lakes (% of grid cell) 7.gghfriv.dat --> Perennial rivers; stream frequency (counts per grid box) 8.gghglac.dat** --> Glacier ice, including shelf ice excluding pack ice (% of grid cell) for this subset all values are 0 but the file was included for sake of completeness. 9.gghilak.dat** --> Intermittent water bodies (% of grid cell) 10.gghiriv.dat --> Intermittent rivers; stream frequency (counts per grid box) 11.gghland.dat** --> Exposed land not covered by swamp, intermittent water bodies, glacier ice, sand dunes, saltmarsh or salt flats (% of grid cell) 12.gghms05.dat --> 5 percent land mask; value of 1 is assigned where the sum of gghdsrf.dat, gghglac.dat, gghsflt.dat, and gghilak.dat exceeds 5%, elsewhere value is 0. 13.gghrice.dat --> Annual average of runoff of glacier ice (kg m^-2 yr^-1) for this subset all values are 0 but the file was included for sake of completeness. 14.gghrner.dat --> Estimated root mean square error of gghrnof.dat (%) 15.gghrnof.dat --> Annual average of surface water runoff from land surfaces (kg m^-2 yr^-1) 16.gghsflt.dat** --> Salt flats (% of grid cell) 17.gghsltw.dat** --> Saltwater, whether marine or terrestrial (% of grid cell) 18.gghsmrs.dat** --> Saltmarsh (% of grid cell) 19.gghswmp.dat** --> Swamp, marsh, and other wetlands (% of grid cell) * Categorical data, go to Legend section of this document for further information. ** The sum of these nine terrain types (land, flak, swmp, sltw, ilak, glac, dune, smrs, sflt) is 100 for each grid cell. ========================================================================= ASCII File Information ---------------------- The data files are in ASCII Grid format for ArcInfo. Each file contains a single ASCII array with integer values. Coordinates listed below are in decimal degrees. Rows 40 Columns 55 UpLeftX 5 UpLeftY 5 LoRightX 60 LoRightY -35 cellsize 1 Projection geographic The ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order. The file format is: {NCOLS xxx} {NROWS xxx} {XLLCORNER xxx} {YLLCORNER xxx} {CELLSIZE xxx} {NODATA_VALUE xxx} row 1 row 2 . . . row n where xxx is a number, and the keyword NODATA_VALUE is optional and defaults to -9999. Row 1 of the data is at the top of the grid, row 2 is just under row 1 and so on. The end of each row of data from the grid is terminated with a carriage return in the file. To import this file into ArcInfo use the following command at an ARC prompt: ASCIIGRID {in_ascii_file} {out_grid} {INT | FLOAT} Arguments: {in_ascii_file} - the ASCII file to be converted. {out_grid} - the name of the grid to be created. {INT | FLOAT} - the data type of the output grid. INT - an integer grid will be created. FLOAT - a floating-point grid will be created. Binary File Information ----------------------- Each ASCII data file has also been converted into a binary image file that can be viewed in any standard image viewing package. The files are single-byte images, no header, 55 columns by 40 rows. Missing data (ASCII -9999) have been converted to the maximum value of 255. ========================================================================= Procedure Used to Create the Southern Africa Subset --------------------------------------------------- The original data were obtained and read following the directions in the original documentation. The data were converted to ASCII arrays and then imported into ArcInfo using the ASCIIGRID command. Using GRID (a raster- or cell-based geoprocessing toolbox that is integrated with ArcInfo) the SETWINDOW command was used to define the subarea of interest. This subarea was defined by identifying the bounding coordinates as follows: x_min 5 y_min -35 x_max 60 y_max 5 The "snap_grid" option of the SETWINDOW command was used. This snaps the lower- left corner of the specified window to the lower-left corner of the nearest cell in the snap_grid and snaps the upper-right corner of the specified window to the upper-right corner of the nearest cell in the snap_grid. In this case the snap_grid is an original data grid. The purpose of this is to ensure the proper registration of the newly set analysis window. The command format used is as follows: SETWINDOW x_min y_min x_max y_max original_grid Once the window was set, creating the new grid was simply a matter of setting the new subset grid equal to the original grid. subset_grid = original_grid An ASCII array was created from the new subset grid using the GRID command GRIDASCII. file.dat = GRIDASCII(subset_grid) ========================================================================= Legend & Additional Sources of Information ------------------------------------------ The following legends are used in the original data for the categorical fields: ****bas1.dat**** 32: no land 48: no runoff 49: internal (local/regional) 50: Arctic Ocean 51: Atlantic Ocean 52: Mediterranean Sea 53: Indian Ocean 54: Pacific Ocean 65: Caspian Sea 66: Aral Sea 67: Lake Balkhash 68: Lop Nor 69: Helmand/Seistan 70: Lake Chad 71: Makgadikgadi 72: Lake Eyre 73: Abbe 74: Assale 75: Blanche 76: Bulloo 77: Eyasi 78: Frome 79: Gholkarteniz 80: Issyk Kul 81: Mar Chiquita 82: Nazas 83: Rudolf 84: Rukwa 85: Poopo 86: Tengiz 87: Urmia 88: Van 89: Uvs Nor 90: Hyargas Nor 91: Tsaidam ****bas2.dat**** 32: No land 48: No runoff 49: Internal drainage 50: Arctic Ocean 51: Atlantic Ocean 52: Mediterranean Sea 53: Indian Ocean 54: Pacific Ocean 65: Caspian 66: Aral 67: Balkhash 68: Lop Nor 69: Helmand-Seistan 70: Chad 71: Makgadikgadi 72: Eyre 73: Abbe 74: Assale 75: Blanche 76: Bulloo 77: Eyasi 78: Frome 79: Gholkarteniz 80: Issyk Kul 81: Mar Chiquita 82: Nazas 83: Rudolf 84: Rukwa 85: Poopo 86: Tengiz 87: Urmia 88: Van 89: Uvs Nor 90: Hyargas Nor 91: Tsaidam 97: Anabar 98: Back 99: Churchill (Manitoba) 100: Colville 101: Hayes 102: Indigirka 103: Kazan 104: Khatanga 105: Kolyma 106: Lena 107: Mackenzie 108: Nelson 109: Ob 110: Olenek 111: Onega 112: Pechora 113: Pyasina 114: Severnaya Dvina 115: Albany 116: Taymyr 117: Thelon 118: Yana 119: Yenisei 120: Pur-Taz 121: Parana 122: Moose 123: Alabama 125: Brazos 128: Amazon 129: Chubut 130: Churchill (Nfld) 131: Cuanza 132: Cunene 133: Douro 134: Ebro 135: Elbe 136: Essequibo 137: Gambia 138: Garonne 139: Jequitinhonha 140: Koksoak 141: Loire 142: Magdalena 143: Mississippi 144: Neva 145: Niger 146: Oder 147: Ogoue 148: Orange 149: Orinoco 150: Parnaiba 151: Rhine 152: Rio Grande 153: Saguenay 154: Sanaga 155: Sao Francisco 156: Senegal 157: St Lawrence 158: Tocantins 159: Uruguay 160: Vistula 161: Volta 162: Zaire 163: Zapadnaya Dvina 164: Danube 165: Dnepr 166: Dnestr 167: Don 168: Nile 169: Rhone 170: Brahmaputra 171: Euphrates 172: Ganges 173: Godavari 174: Indus 175: Irrawaddy 176: Juba 177: Krishna 178: Limpopo 179: Mahanadi 180: Murray-Darling 181: Rufiji 182: Salween 183: Tigris 184: Zambezi 185: Amur 186: Anadyr 187: Chao Phraya 188: Colorado 189: Columbia 190: Fraser 191: Hwai 192: Hwang Ho 193: Kuskokwim 194: Liao 195: Mekong 196: Pearl 197: Red 198: Rio Grande de Santiago 199: Yangtze 200: Yukon 201: Kura 202: Ural 203: Volga 204: Amu Darya 205: Syr Darya 206: Cooper 207: Warburton 208: Bandama 209: Save 210: Ruvuma 220: Baltic 221: Black Sea 222: Red Sea 223: Persian Gulf 224: Hudson Bay-Foxe Basin 225: Gulf of Mexico 226: San Francisco Bay ****gghcryo.dat**** 32: water without ice cover 48: permafrost absent or extremely restricted 49: permafrost restricted 50: permafrost common 51: permafrost ubiquitos 53: permanent sea or lake ice 54: seasonal sea or lake ice 55: ice shelf 57: ice sheet It is highly recommended that you review the original documentation for this data set for more specifics. It can be downloaded from the following anonymous ftp site at Trent University: ftp://ftp.trentu.ca/pub/gghydro/ ------------------------------------------------------------------- ORIGINAL DATA SET CITATION ------------------------------------------------------------------- Cogley, J.G., 1998, GGHYDRO -- Global Hydrographic Data, Release 2.2. Trent Climate Note 98-1, Department of Geography, Trent University, Peterborough, Ontario, Canada. Data available on-line at ftp://ftp.trentu.ca/pub/gghydro/