New York State Office of Cyber Security
Geographic Information Systems Clearinghouse
Frequently Asked Questions
General Help Using Digital Orthoimagery
- Files to Download
- File Formats
- File Naming Conventions
- Viewing the Orthoimagery
- Orthoimagery Indexes
- Useful Software
- What is digital orthoimagery (DOI)?
Digital orthoimagery - a remotely-sensed digital picture, stored in a raster data format. It is a georeferenced image prepared from a vertical photograph or other remotely-sensed data in which displacement of objects due to sensor orientation and terrain relief have been removed. Digital orthophotos combine the image characteristics of a photograph with the geometric qualities of a map.
- Why is the digital orthoimagery
I downloaded not displaying properly?
Users must download the .sid or .jp2 and either the .sdw, .j2w or .tab file to display the digital orthoimagery within a GIS package. MapInfo users need to download the associated .tab file, along with each downloaded ortho. ESRI users need to download the associated .sdw or .j2w file, along with each downloaded ortho. The image files and the support files must
- Why did the file format of the digital orthoimagery
change?
For 2006, the file format of the orthoimagery has been changed to JPEG 2000. This is an open standard format with better resolution at similar levels of compression. This format was agreed upon by the New York State GIS Coordination Program’s Remote Sensing Workgroup.
- Why does the color infrared (CIR) orthoimagery
colors appear the way they do?
This imagery is based on color infrared aerial photography with red tones indicating vegetation vigor.
- Are the orthos for the entire state available
at no cost? Are they for sale?
The NYSDOP has covered every portion of the state at least twice since 2000. In addition the entire state was photographed as part of the NAPP 1 Meter 1994 - 1999 program. Please refer to the NYS Digital Orthoimagery Program status for new digital orthoimagery. All this imagery and their associated GIS files are available for download at no cost.
- Can I change the coordinates appearing
at the bottom of the application?
The coordinates displayed reference the location of the cursor in the map window. Use the drop-down menu to change the coordinate system referenced. The options are: Lat/Long; UTM(Universal Transverse Mercator); SP (New York State Plane).
[More Information] - View the on-line help within the application for more details
- What do the coordinates refer to?
The coordinates represent the cursor's location in the map window, displayed in latitude and longitude.
- How accurate are the coordinates?
The coordinates are reported to four decimal places, corresponding to approximately 10 meters in New York State (longitude 8 meters, latitude 11 meters near the state's geographic center). The accuracy of the features selected in the map window depends on the resolution of the orthoimagery being viewed. The NYS Statewide Digital Orthoimagery 1 Meter (CIR 1994 - 1999) has a spatial accuracy of approximately 10 meters, while the spatial accuracy of the NYS Statewide Digital Orthoimagery Program 2000 (Nassau and Rensselaer counties) ranges from 4 to 8 feet.
- What projection is used for the
NYS Statewide High Resolution Digital Orthoimagery and the
1 Meter 1994 - 1999 Color Infrared?
For more information on projection, select to the "Data Set Description" button at the top of the page for each orthoimagery data set. The projection will be described within the data set description.
- How can I reproject to a different projection?
The current application does not allow for conversion to other projections. Some commercial software is capable of doing this.
- What do the extensions *.sid, *.jp2, *.tab,
*.sdw, *.j2w and *.aux stand for?
".sid" is the extension for files created in the proprietary MrSID compression format. MrSID software is a product of Lizardtech, Inc.
".jp2" is the extension of files compressed in the JPEG 2000 format, an open standard format.
".tab" is the MapInfo file extension for georegistration files that are used in conjunction with ".sid" files to orient a MrSID-compressed file to its real world location. MapInfo is GIS software that is a product of MapInfo Corporation.
".sdw" is the ArcView file extension for georegistration files that are used in conjunction with ".sid" files to orient a MrSID-compressed file to its real world location. ArcView is GIS software that is a product of Environmental Systems Research Institute (ESRI).
".j2w" is the world file used for georegistration of the JPEG 2000 files to real world coordinates.
".aux" is the auxillary files used with ESRI ArcGis.
- What software can I use to view the orthoimagery?
The most widely-used GIS software offer capabilities to view JPEG 2000 & MrSID-compressed images within their packages. The georegistration file(s) must be in the same directory as the ".sid" or ".jp2" image files in order to properly register the files to real world location. Please visit our "Useful Software" for free software downloads to view the imagery.
- Why am I having problems with .sid or .jp2
files in ESRI's ArcGIS (9.x)?
Please use the GIS Help Desk for assistance.
- Can I add other data layers over the orthos?
Yes, for ESRI users, the other layers need to be registered to the same datum and projection as the orthoimagery or in latitude and longitude.
[More Information] - View the on-line help within the application for more details
- How can I use the orthoimagery in a GIS application?
The orthos are most often used as a backdrop with other data layers on top. For example, parcel boundaries can be layered on top of the orthos.
- What is a seamless table and how is it used?
A seamless table is comprised of 4 MapInfo files. There is a seamless table associated with all the sid or jp2 files for each geographic area. The seamless table files MUST be in the same directory as the individual *.tab and *.sid or .jp2 files. Open a seamless table as you would open any table in MapInfo. For more information, consult the Help section in MapInfo software.
- What is an image catalog and how is it used?
There is an image catalog, 00IC*.dbf file, associated with of all the sid files for each geographic area. The image catalog uses a system environment variable, $NYSDOP. In order to use an image catalog, the user must set the system environment variable on their machine before using the ESRI software.
General Help
- MapInfo Professional or MapInfo ProViewer users need to download
both the *.sid file and the *.tab file associated with each tile.
ESRI ArcView or ArcExplorer users need to download both the *.sid
file and the *.sdw file associated with each tile.
- To view the orthoimagery using an image viewer or image processing
software, only the *.sid is needed.
For information on how to use these files refer to the "Viewing the Orthoimagery" section
For information on how to use these files
refer to the "Viewing the
Orthoimagery" section.
(* MapInfo and MapInfo ProViewer users need the
*.sid and the *.tab file to view
the orthoimagery. ArcView & ArcExplorer users
need the *.sid and *.sdw to view
the orthoimagery)
NYSDOP High Resolution Statewide Imagery
State Plane Coordinate Tiles
z_eeeennnn_pp_hhhhh_fff_yyyy.ext
Where:
- "z" = State Plane Zone (e = East, c = Central, w = West, l = Long Island)
The Easting and Northing coordinates are concatenated- "eeee" = Truncated Easting coordinate of southwest corner of the tile. The last three digits are dropped, since they will always be "000." Leading zeros are used where appropriate.
- "nnnn" = Truncated Northing coordinate of the southwest corner of the tile. The last three digits are dropped, since they will always be "000." Leading zeros are used where appropriate.
- "pp" = Image pixel size in inches
- "hhhhh" = Flying height in feet
- "fff" = Film or image type (pan = panchromatic, col = natural color,
cir = color infrared- "yyyy" = Year of image capture
Example:
e_03451234_12_14400_cir_2001.extZone = NY State Plane East Zone
Easting = 345,000 feet
Northing = 1,234,000 feet
Pixel size = 12 inches (1 foot)
Flying height = 14,400 feet
Film type = Color infrared
Year = 2001
NAPP 1 Meter Resolution Statewide Imagery
UTM Coordinate Tiles Quadname
Quarter_tile.extension
Where:
- "Quadname" = Parent quadrangle name derived from the Dept. Of Transportaton (DOT) naming convention, including areas outside of New York if available. USGS names were used if a DOT name was not available
- "Quarter" = The Quadrant of the Quadrangle relative to compass directions, ie NW, SE
- "_tile" = The quarter section of the quarterquad, numbered beginning in the upper left section and proceeding clockwise
Example:
BrewsterNE_tile0.sid
There are several image viewing programs available to use for
the purpose of viewing our orthoimagery. See our "Useful
Software" page to link to free software available for
download. Each of the software programs has help menus and documentation
on their use.
In addition to viewing orthoimagery, popular GIS software programs
can use the orthoimagery for general reference and orientation,
feature identification, and the measurement of distance and area.
The following are general tips to get started:
MapInfo Professional
- The MrSid raster engine handler must be installed with the software
- View the orthoimagery by selecting and opening the .tab file
- Some of the orthoimagery have default zoom levels, the zoom levels can be removed or changed in the Map > Layer control
- Vector data layers can be added by opening associated .tab
files, vector data layers can be re-projected if they are not
in the same projection as the orthoimagery (raster) files.
Using Seamless Tables: A seamless table is comprised of four MapInfo files. There is a seamless table associated with all the sid or jp2 files for each geographic area.
The seamless table files MUST be in the same directory as the individual *.tab and *.sid or *.jp2 files. Open a seamless table as you would open any table in MapInfo. For more information, consult the help section in MapInfo software.
ESRI - (ArcView, ArcInfo)
- The MrSid Image Support Extension must be loaded from the extensions menu first.
- When adding the orthoimagery as a theme, the "Data Source Type" should be Image Data Source, not Feature Data Source.
- View the orthoimagery by selecting and opening *.sid or *.jp2 file.
- Vector data layers can be added by opening associated files,
vector data layers can be re-projected if they are not in the
same projection as the orthoimagery (raster) files. Make sure
the "Data Source Type" is Feature Data Source
when adding the vector files.
Using Image Catalogs:
There is an image catalog, 00IC*.dbf file, associated with of all the sid files for each geographic area. The image catalog uses a system environment variable, $NYSDOP. In order to use an image catalog, the user must set the system environment variable on their machine before using the ESRI software.
For additional information using and viewing digital orthoimagery,
please go to the Introduction
to Digital Orthoimagery on-line training presentation
for reference.
Each digital orthoimagery data set has a corresponding index to the tiles of orthoimagery. There may be more than one index if there are different film types and/or the orthoimagery in the application is available in more than one coordinate system. The indexes contain Information such as the tile name, the source date, and the x and y coordinates. The indexes can be viewed using GIS software.
NYSDOP High Resolution Imagery - Refer to the County Direct Download page for the individual county indexes.
NAPP 1 Meter Resolution Imagery - Refer to the NAPP Region Direct Download individual tile page for the indexes.
Attribute Dictionary for NYSDOP High Resolution Imagery
and NAPP 1 Meter Resolution Imagery:
| Tile_Name: | The image registration file (MapInfo format used to dynamically access the imagery files). |
| *.sid (or *.jp2) | The image size in kb |
| *.sdw (or *.j2w) | The file size in kb |
| *.tab | The file size in kb |
| *.aux | The file size in kb |
Listed below are links to "free" software to use to view or download the orthoimagery files.
- ArcExplorer - ESRI's free "lightweight GIS data explorer," which allows users to display and query (but not create) GIS data sources.
- ArcExplorer
Version 1.1 Import Utility - This utility converts ArcInfo interchange
files ".e00" into ArcInfo coverages, which then can be used in ArcExplorer.
You'll find this useful for many of the free data sets that you can download
from the Web.
- DAP - Download Accelerator
Plus - This free download utility fully integrates into your browser
and may speed your download up to 300% Faster. It is very easy to use.
- ER
Viewer - From ER Mapper, a free "easy to use" image viewer featuring
interactive roaming and zooming of very large image files. ER Viewer supports
a wide range of image formats and is OLE-enabled, for viewing images inside
Windows applications.
- Geomatica -
PCI Geomatica offers Geomatica, a free viewing environment for imagery and
graphical bitmaps.
- IrfanView - IrfanView
is a very fast, small, compact and innovative FREEWARE (for non-commercial
use) graphic viewer for Windows 9x/ME/NT/2000/XP/2003/2008/Vista/Windows 7.
- MapInfo
ProViewer - This free viewer allows users to display tables and workspaces
created with MapInfo. An add-on support is available to use with LizardTech
MrSid format images.
- ExpressView -
A free application from LizardTech that allows users to view imagery in MrSid
format.
- TNTatlas is
a free Geodata viewing tool for Mac OS X 10.3x or 10.4x and Windows XP/2000/2003/2008/Vista/Windows 7.
Geodata files currently supported include shapefiles, DWG, DGN, DXF, JPEG,
JP2, TIFF, GeoTIFF, PNG, ECW, and MrSID formats. TNTatlas also has features
for querying, measurement, printing, sketching of the displayed geodata.
You can even plug a GPS unit and track yourself realtime, or get a profile
from your 3D elevation raster using TNTatlas.
- Tucows is
a listing of download managers.