Download presentation
Presentation is loading. Please wait.
Published byBuck Kelly Modified over 6 years ago
0
Lecture 04: Data Storage and Representation & Access to Spatial Data
Geography 128 Analytical and Computer Cartography Spring 2007 Department of Geography University of California, Santa Barbara
1
Storage Media Traditionally, the paper map has performed a storage function for spatial information Computer cartography requires information to be digital and stored explicitly Storage is increasingly distributed over networks Many mapping programs require local storage of data Cost and size restraints now less important
2
Evolution of Storage Media
3
Physical Storage Bit - the most basic information unit in a binary system (1 / 0) 1 Byte = 8 bits Binary (2-based), Decimal(10-based), and Hexadecimal (16-based) System Binary Operator – AND, OR, NOT Data on a disk -Sectors, Tracks, Platters File system – File, Directory
4
Maps as Numbers Map data is stored in the computer’s memory in a physical data structure (i.e. files and directories). Files can be written in binary or as ASCII (American Standard Code for Information Interchange) text. Binary is faster to read and smaller, ASCII can be read by humans and edited but uses more space.
5
ASCII Table
6
ASCII Table (extend)
7
Storage Efficiency and Data Compression
Cartographic data sets are typically large Need to reconfigure data formats, structures etc. Seek to retain information content, lose volume. Is redundancy necessary?
8
Rasters vs. Vectors
9
Storing Coordinates (Vector)
Physical Compression 4,513,410 m N;587,310 m E; Zone 18,N (32 characters, 15 digits) (13 digits, one space) Need metadata F 0F 42 3F (six bytes) Logical Compression Drop last two digits (10 ASCII or 2 bytes per coordinate)
10
Raster data Compression
Run-length encoding Quad-trees …
11
Data Storage Formats for Cartography - U.S. Geological Survey
DLG – Digital Line Graphs (1:24,000; 1:100,000; 1:2,000,000) DEM – Digital Elevation Model (1:24,000; 1:250,000) GIRAS – Land-use and Land-cover Digital Data (1:100,000; 1:250,000) GNIS – Digital Cartographic Text
12
Data Storage Formats for Cartography - U.S. Geological Survey
USGS DLG format
13
Data Storage Formats for Cartography - U.S. Geological Survey
USGS 1:250,000 3-arc second DEM format (1-degree block)
14
Data Storage Formats for Cartography - U.S. Geological Survey
USGS 1:24, meter DEM format (7.5-minute quadrangle)
15
Data Storage Formats for Cartography - CIA World Data Bank
WDB I (1:12M base, 100K points) WDBII (1:3M base, 6M Points) DCW 1:1M base- 4 CDs, 14 layers DMAs VPF
16
Data Storage Formats for Cartography - Industry “Standard” Vector Formats
Vector formats are either page definition languages or preserve ground coordinates. Page languages are HPGL, PostScript, and AutoCAD DXF. Proprietary GIS Formats Arc/Info, ArcGIS MapInfo …
17
Data Storage Formats for Cartography - Industry “Standard” Raster Formats
Most raster formats are digital image formats. Most GISs accept TIF, GIF, JPEG or encapsulated PostScript, which are not geo-referenced. GeoTIFF is true geographic data format
18
Finding Existing Map Data
Map libraries Reference books State and local agencies Federal agencies Commercial data suppliers e.g. GeographyNetwork.com, Rand McNally, Thompson, NAVTEQ, maps.com
19
Existing Map Data Existing map data can be found through a map library, via network searches, or on media such as CD-ROM and disk. Many major data providers make their data available via the World Wide Web, a network of file servers available over the Internet. GIS vendors package data with products.
20
Commercial vendors
21
Federal Data Agencies U.S. Geological Survey (USGS)
National Oceanic & Atmospheric Administration (NOAA) Census Bureau National Geospatial-Intelligence Agency (NGA) Environmental Protection Agency (EPA) many more...
22
National Spatial Data Infrastructure
23
Geodata.gov
24
National Spatial Data Clearinghouse
25
USGS: National Mapping
26
National Map Viewer
27
DOQQ (Digital Orthophoto Quarter Quadrangle ) plus DLG streets
28
DRG (Digital Raster Graphics) plus DLG streets
29
Seamless data download
30
Other components of the NSDI (Portals, standards, services, data)
Geospatial Onestop Geography Network EROS Data Center FGDC: Standards Alexandria Digital Library State data centers e.g. Teale in CA MapQuest NAVTEQ, etc. Counties, municipalities, universities, tribes, etc.
31
U.S. Bureau of the Census
32
National Oceanic and Atmospheric Administration (NOAA) Weather and other data
33
Eros Data Center Distributed active archive center Sioux Falls, SD
Operated by USGS
34
US GeoData ftp access to DEM DLG GNIS GIRAS etc.
35
GNIS Feature locations
36
GIRAS Land Use and Land Cover Data
37
GIRAS into Arc/Info (GIRASARC)
38
Terrain data DEM DLG Contours DCW Contours
39
Next Lecture Spatial Data Structure
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.