GIS DATA INPUT USING SCANNERS AND DIGITIZERS Charles Redd & Nathan Miller Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.   Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion. Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience. 9/17/2018

First Some History 9/17/2018

The Beginning ? GIS was born in Canada in the 1960’s to manage Canada’s large natural resources. The success of the merger of computers, database, and mapmaking was a big success. 9/17/2018

Did GIS Make 2,500 plus Years of Documents & Mapmaking Suddenly Obsolete ? From cave paintings to satellite images 9/17/2018

Hard Copy Data with GIS Significance Maps Aerial Photos Tables of spatial information (coordinates) Tables of Non-spatial information attributes Engineering and Architectural plans Land and Geological Surveys Caveman Drawings? Maybe 9/17/2018

How can we use pre-GIS data and non-digital data in our GIS Digitize existing graphical information! Some of the first methods to digitize graphical information involved overlaying the map with a grid marked on a clear sheet of Mylar. Information that was within each grid was visually observed and entered by keyboard into the GIS. Attribute data from existing tables was hand entered. There must be a better way! 9/17/2018

Manual Digitizing ? The majority of spatial data entered into a GIS is from manual digitizing. 9/17/2018

Manual Digitizing The digitizing tablet and table allow information to be traced from an existing map or graphic. Three different types of tables or tablets exist. (1) Acoustic – the digitizing pen emits a high frequency sound that is received by microphones at the corners of the work area, triangulation is used to calculate the x and y coordinate of the pen. 9/17/2018

GTCO CalComp Sonic Digitizer 9/17/2018

Types of Digitizers (Continued) (2) Resistivity uses two charged pads separated by a thin air gap, x and y coordinates are determined when the pads make contact. (3) The most widely used in large scale digitizers is the electronic digitizing tablet. Embedded below the surface of the table or the tablet is a grid of wires that measure the strength of the signal from the puck or the pen 9/17/2018

Qualities of a Digitizer Stability The ability of the digitizer to maintain a value as the puck remains in one place. Repeatability Precision Good digitizers accurate to 0.001 inch 9/17/2018

Qualities of a Digitizer #2 Linearity the ability to be within a specified distance of the correct value Good digitizers are able to have a linearity of 0.003 inch over 60 inches Skew The ability to produce coordinates in a true rectangle. 9/17/2018

Digitizing Procedures The Map is fixed to the digitizing table. Three or more control points are digitized. Easily identified points (intersections of major streets, major peaks, points on coastline) These coordinates will be known or verified The digitizing area is registered to the map area. Digitizing the map can be done in two ways. In point mode , the operator identifies the points captured explicitly by pressing a button. In stream mode the points are captured at regular intervals (time or distance) 9/17/2018

Digitizing Procedures (cont) Point mode is done subjectively by the operator (no two operators will digitize the same). Stream mode generates a large number of points, many of which will be redundant. Most digitizing is done in point mode. 9/17/2018

Advantages of Digitizing Low initial capital cost Flexible and adapts to different types of data Easily mastered skill Digitizing devices are reliable Generally the quality of data is high 9/17/2018

Digitizing Vendors Altek Calcomp Didger GTCO Kurta 9/17/2018

Problems with Digitizing Paper maps are unstable, they stretch or shrink, sometimes while they are on the digitizing table. The accuracy depends on the dedication of the operator and his training and skill. Accuracy also depends on the quality of the source documents. Paper maps weren’t prepared “digitally” correct, but to visually impart information, for example if railroads, highways and tunnels pass through a mountain pass the pass may be drawn larger to accommodate the drawing. 9/17/2018

Scanning Technology Converts paper maps into digital format by capturing features as cells, or pixels. Cells are captured using a scanner head made up of photosensitive cells. Advanced large format scanners have heads with 8000 photosensitive cells Each sensor is able to record a pixel rated between 0 (black) to 255 (white) and any graytones between. 9/17/2018

Color Scanning Technology Color images use the same technique but the image is scanned for red, blue and green. Older scanners required the image being scanned to pass the scanning head in three passes. Vectorization often requires color scanning 9/17/2018

Color Scanning Technology Filters allow the head to pass the image once scanning all three colors at once The latest technology: full width, single line, sensor array scanning uses a line of LED’s which capture the image LED scanners can create images using 16.8 million colors at speeds several times faster than previously obtained. 9/17/2018

Scanning Problems Higher resolutions aren’t always the answer to better data; often the additional “noise” and resulting clean up of data can cause higher resolution to not be the best solution, a balance between detail and additional manual clean-up must be struck. Paper maps are not “dimensionally stable” and a great deal of variation occurs as the maps age. Documents must be clean (no smudges or extra marks or lines). 9/17/2018

Scanning Problems #2 Text may accidentally be scanned as line features in automatic feature recognition. Specialized symbols (for example marsh or asphalt) may not be detected as such. 9/17/2018

Large Format Monochrome Scanners IDEAL   Large Format Monochrome Scanners Model Price max dpi Paper Size Speed FSS 4300DSP $6,675 200 36 in. 15 sec. FSS 8300DSP $10,425 800 17 sec.@200 dpi FSS 12300DSP $11,925 1200 25 sec.@200 dpi FSS 18300DSP $13,425 1800 34 sec.@200 dpi Super Wide 2250 400 50 in. 3 in./sec. Super Wide 2251 $14,925 6 in./sec 9/17/2018

Model Price max dpi Paper Size Speed ANAtech   max dpi Paper Size Speed ANAtech   Binary & Grayscale Scanners Evolution 4 $10,000 400 36 in. 3"/sec @ 200 dpi Evolution 8 $11,000 800 Evolution Pro $12,500 6.4"/sec @ 200 dpi High Resolution Monochrome Scanners 1270 Digidot $50,000 1270 27 in. Unknown Eagle 4225 $55,000 2540 42 in. 9/17/2018

Model Price max dpi Paper Size Speed Large Format Color Scanners   max dpi Paper Size Speed Large Format Color Scanners   ESC 5010 DSP $11,175 500 36 in. 36 sec.@200 dpi FSC 8010 DSP $14,925 800 48 sec.@200 dpi Large Format Color Scanners   Colortrac 5480 $31,000 800 54 in. 1.5"/sec. @ 200dpi Eagle 6250C $142,000 1000 62 in. Unknown 9/17/2018

Vendors for Scanners Widecom Scanners Anatech Scanners www.widecom.com/ Anatech Scanners www.anatech.com/ Vidar Systems Corporation www.delinfotek.com/ Abakos Digital Images www.abakos.com.au/ Contex Scanning Technologies www.caddcentreindia.com/ 9/17/2018

Digitizer or Scanner Scanners Speed and ease Raster data without intelligence; manual or automatic vectorisation possible. Usually produces large files that need compression Hardware is expensive Digitizers Labor intensive Requires skilled operator Vector (intelligent) data Hardware less expensive 9/17/2018

Scanning & Digitizing Input Errors Incompleteness of the spatial data; missing points, line segments, and polygons. Location placement errors of spatial data; careless digitizing or poor quality of the original source. Distortion of spatial data; base maps that aren’t scale correct over the entire image or from material stretch in paper maps. 9/17/2018

Scanning & Digitizing Input Errors #2 Incorrect linkage between spatial and attribute data; misplaced labels or unique identifiers being assigned during manual key entry or during the initial setup. Attribute data is wrong or incomplete; missing data records or data records from different time periods. Redundant information, including vertices, text, nodes, and arcs. Incorrect label information and placement. 9/17/2018

Common Spatial Errors Slivers or gaps in the line work. Dead ends, dangling arcs, overshoots and undershoots. Bow ties or weird polygons caused by inappropriate closings of connecting features. 9/17/2018

Data Verification Visual review; usually done by reviewing a check plot (hard copy). Cleanup of lines and junctions; this process is usually done by software and then through manual editing. Check source maps, if additional copies of the same map are available compare them to see if stretching of the map has occurred. Check output drawing to see if text or symbols were read as features if software is used to convert the drawings. 9/17/2018

Examples of Scanned and Aerial images 9/17/2018

Paris 1640 9/17/2018

Paris 2000 9/17/2018

Notre Dame 9/17/2018

Summary of Presentation or…. Things I Learned Preparing this Report Scanning while initially faster may not be the fastest solution for your data input. Source information needs to be carefully assessed before a method of data conversion is selected. The skill and motivation of staff should be evaluated before a method is selected. 9/17/2018

Summary of Presentation or…. Things I Learned Preparing this Report #2 Acoustic or Sonic Digitizers Exist Digitizing can be as accurate as .001 of an inch Color scanners are needed for automatic vectorization 9/17/2018

One Eagle 6250C Color Scanner Costs more than two Dodge Vipers Two Vipers @ $69,225 = $138,450 9/17/2018