**CD-ROM AS MEDIUM FOR LARGE****GEOGRAPHIC INFORMATION FILES**
William W. Wallace,  Janet K. Mencher
National Geodetic Survey, NOAA, Silver Spring, MD 20910
**Abstract**: In June 1993 the National Geodetic Survey chartered a Total Quality ManagementProcess Action Team (PAT) to study the feasibility and practicability of using CompactDisc-Read Only Memory (CD-ROM) as a medium for disseminating large geographic informationdata sets, specifically geodetic control data and related software. This is a case study of the PAT'sprogress. Some of the issues discussed include technical issues involving CD-ROMstate-of-the-art technology and cost, content issues concerning which data and software areappropriate for this medium, distribution issues addressing the target audience, and managementissues concerning personnel and budget. The PAT's study lasted approximately 3 months, andresulted in production of a prototype CD-ROM product which was distributed first to a smallgroup of traditional users of geodetic data for their comments and recommendations. The papercloses with an assessment of the suitability of CD-ROM as a medium for largegeographic/geodetic data sets.
**INTRODUCTION**
Starting in 1992, the National Geodetic Survey (NGS), a division of the National Oceanic andAtmospheric Administration's Coast and Geodetic Survey, began using a Total QualityManagement (TQM) approach to planning and problem solving. Under the guidance of anExecutive Steering Committee, several Process Action Teams (PATs) were formed during late1992 and early 1993 to develop various aspects of a strategic plan for NGS. One of therecommendations that resulted was to study the feasibility and practicability of using CD-ROM asa medium for disseminating large data sets containing geographic/geodetic information.Accordingly, a new PAT was formed to conduct this study. The team charter called for the PATto gather relevant technical information and debate the issues "until substantial agreement isreached."  The primary issues defined in the charter were those of data content, technology,management, and dissemination of a product. All of these as well as some additional points arediscussed in this paper. The deliverable product for the team, assuming that it found CD-ROM tobe a viable option, was a product development plan, describing actions to be taken both todevelop the product and at steady state operations.
Because this is a paper on CD-ROM technology, not TQM approaches to management, we willnot spend time discussing the details of TQM. Suffice it to say that the team agreed on rules ofconduct and operating procedures and followed these throughout the process. We found, as otherteams before and after, that the TQM approach works very well when guidelines are agreed toand followed.
**CONTENT ISSUES**
When team members discussed issues, they were not treated as independent, isolated issues; i.e.,content issues were not discussed completely separately from technical issues. However, for easeof presentation in this paper, we have grouped the topics discussed under the categoriesmentioned. The first category concerns the data and software that would be included on theCD-ROM. Some of the types of questions that we addressed are the following: Should weconsider a product which is issued on a regular basis or should we confine ourselves to a datasampler, designed to demonstrate what is possible and develop user interest? What types ofgeodetic data should be on a CD-ROM? What data elements? What area coverage? What dataretrieval software should be supplied? Should this also be on the same CD-ROM? What about"browsing" software? Visualization (graphics) software? Should an instruction (README) file beincluded on the CD-ROM or should there be separate hardcopy instructions?
Before we address these questions, some description of what is meant by geodetic data isappropriate, since we should not assume that most of our audience is familiar with geodesy.Geodetic data pertain to attributes of geodetic control stations, sometimes called "survey marks"or "bench marks." Over the past 150 years this agency and its predecessors have established over750,000 of these stations throughout the United States to provide precise and accurate horizontal(latitude and longitude) and vertical (height or elevation above a common datum) references forengineers, surveyors, and others requiring accurate positions and heights. Collectively thesestations make up the National Geodetic Reference System (NGRS) which supplies the frameworkto support surveying, mapping, charting, navigation, boundary determination, propertydelineation, infrastructure development, and geographic and land information systems. Examplesof attributes that pertain to these stations include stations' names or designations, latitudes,longitudes, heights, state plane coordinate values, datums used, a description of where the mark islocated and how to reach it, a history of when the mark was recovered and the condition in whichit was found, and a unique identifier that pertains only to that station and ties all station recordsand attributes together in the NGS data base.
As one can easily imagine, the data files containing all of these station records for over 750,000marks are quite large (approximately 4 gigabytes or 4 billion characters). Although there havebeen many types of geodetic data products in the past, the most used (and hopefully useful)product is the NGS "data sheet" which combines the most often requested data elements in aconcise format for each station in a given geographic area. Figure 1 is a sample of a two-pagedata sheet record. Although the data sheet is a concise format, the average station fills theequivalent of nearly two pages, so file sizes even for small geographic areas can still be large. The"standard" medium for disseminating these data sheets for the past several years has been diskette.Often the data are distributed on a county by county basis. On average, one county's data sheetfiles will fit on one high density diskette, although there are areas which require multiple diskettesfor one county. One of the reasons for examining the possibility of CD-ROM (or other highdensity media) for geodetic data distribution is that many users would like to receive an entirestate or several states of data. This can require hundreds of diskettes, which is costly for the userand very time consuming for our data distribution personnel to produce.
We go back now to some of the questions posed on the content issue at the beginning of thissection. Should we consider a "sampler" product initially, or a true, useful data product. Our teamfelt that its members understood the needs and capabilities of its user community sufficiently wellthat it was comfortable issuing a CD-ROM product following the format of an existing product,rather than exhausting the considerable resources that would be necessary to generate a "new"product to be called a "sampler." Since the digital data sheet is a well-established product with asuite of viewing and extraction tools and existing documentation, the team agreed that the basiccontent of a regularly issued CD-ROM would be the digital data sheet format. The next questionto be answered was "How much data should we put on a CD-ROM?" One state? Several states?The entire country?
The team considered but rejected the possibility of putting the entire U.S. on a single CD-ROM.This would require data set compression, and users would be required to have sufficient diskspace to hold decompressed files. In addition, few users would be interested in so much data.Most of NGS' traditional users work in areas covering a few counties, or at most a few states.Since a CD-ROM holds 600 to 680 megabytes(MB) of data, depending upon the type of CDchosen, we set a criterion of 520MB of digital data sheet information as the limit to put on asingle CD-ROM. This leaves room for indexes, search and retrieval software, and perhaps somefuture data sets and/or software that would be desirable to add. Given this limit, the U.S. waspartitioned into five regions as shown on Figure 2. The estimated file sizes are shown for eachregion. Because geodetic control is generally more dense in coastal areas, the CD-ROMs for theNortheast, Southeast, and West regions cover a smaller geographic area than the North and SouthCentral regions.
The remaining content questions concern the types of presentation software and instructions toput on the CD-ROM. The existing digital data sheet product distributed on diskette haspresentation software called "DSX" which allows several options for viewing the data. The datafile, called "DSDATA," is an ASCII file containing data sheets for one county in alphabeticalorder. On the CD-ROM there would be an index and multiple file names to reflect the CD-ROM'smultiple counties in many states, instead of one county per diskette. Since the data are ASCIIfiles, the CD-ROM should be directly readable on an IBM PC-compatible computer, runningDOS, and also on most MacIntosh and UNIX platforms. However, in order to use the DSXpresentation software on a system other than DOS, the source code (which is included on theCD-ROM) for DSX would have to be run through an ANSI C language compiler for whateverplatform one is using. The "README" file used on diskettes would have to be modified to reflectthe mentioned changes for CD-ROM, but this is a relatively minor task. The team also discussedsome possible future additions for the CD-ROM product. These are discussed in the section ofthis paper called "Product Development Plan."
**TECHNICAL ISSUES**
Although the team charter called for us to look at CD-ROM as a medium, we also examined othermedia, both magnetic and optical. Space does not allow us to include all of the details discussedby the team, but highlights are included here.
**Magnetic versus Optical Technologies**
Examples of magnetic media are floppy and hard disks and magnetic tape. Magnetic media use amagnet in the read/write head to change the polarity of bits on the magnetic media from 0 to 1 or1 to 0. The head is bidirectional, i.e., it can change bits from 0 to 1 or 1 to 0 in one pass. Theprimary advantage of magnetic hard disk drives is speed. Hard disks are very fast, with averageaccess times of 20 milliseconds or less. A major disadvantage is that all magnetic media can beaffected by stray magnetic fields, thus scrambling of information can occur.
There are three types of optical storage technologies - WORM (Write Once Read Many),rewritable optical, and CD-ROM. Optical disc technology uses a laser beam to read/write to adisc. Because the light from a laser beam is more focused than magnetic read/write heads, moredata can be squeezed onto an optical disc in the same relative space. Some general advantages ofthis technology over magnetic are the following:
They are more durable than magnetic media - most optical discs are made of polycarbonate, thesame plastic used in bullet-proof windows.
They have greater storage capacity, are more reliable, removable, and cost far less per megabyte.
Head crashes don't occur because the optical head is held 1000 times farther away from the discsurface than the "flying" magnetic head.
Contamination is not much of a concern since the laser beam is focused on the recording layerbelow the clear plastic, allowing the drive to read through most scratches and fingerprints.
The primary disadvantage of optical technology is speed. Access time is slower than hard disksdue to the weight of the optical head with its laser, lenses, and mirrors.  At the present time,access times for optical discs are two to six times slower than high performance disk drives.Because of this, optical drives are not expected to replace hard disks within the next several years.
**Media Selection**
Among optical technologies, there are many reasons for choosing CD-ROM over WORM orrewritable for our application:
There is a well established, accepted standard for CD-ROM technology known as ISO 9660. Thestandard defines the media size and characteristics, physical data layout on the disc, errorcorrection, disc rotation speed, and other parameters. This means that every CD-ROM readerwhich is ISO 9660 compliant can read a CD-ROM. Currently, there are no international standardsfor WORM technology. WORM discs come in a variety of sizes and densities. There are so manyproprietary WORM drives that accessing information from a WORM disc written on a differentdrive is nearly impossible.
Files can be created on a CD-ROM that are operating system  independent. This means that anISO 9660 disc works identically on a Personal Computer (PC), MacIntosh, or SUN workstation(UNIX).
CD-ROM drives will be backwardly compatible. This means that CD-  ROM readers will be ableto read a CD-ROM made today on the computers of tomorrow. This backward compatibility isspecified in the ISO 9660 standard.
CD-ROMs as a medium are very durable. Only severe damage will make a CD-ROM unreadable.Environmental hazards like magnetic fields, X-rays, moderate heat or extreme humidity, as well asold age, do not hurt CD-ROM data as they do magnetically stored data. CD-ROM discs are alsoimmune to infection by computer viruses.
CD-ROM technology is widely accepted. Although the other optical   technologies areinteresting, none is as widespread as CD-ROM, and it is not likely that any of them will replaceCD-ROM in the marketplace in the foreseeable future.
CD-ROM is appropriate for products intended to have a wide distribution. Once you retrieve andorganize data on a CD-ROM  glass master, you can replicate the master by stamping out otherCD-ROMs from it. This means customers can get the data quickly, easily, and cost effectively.Because you can only write once to a CD-ROM, no one can overwrite data on it. CD-ROMs arealso well suited for the distribution of large amounts of data, since a single CD-ROM can hold asmuch as 680MB of data. 
There are several steps involved with making CD-ROMs.The first involves putting data andsoftware in the desired form for the final CD on a medium from which a "glass master" can bemade at a manufacturing site. This can be done on magnetic tape or removable hard disk, butthese technologies have been outdated by desktop mastering hardware and software which can bepurchased for as little as $5,000 to $8,000. The recorders used for this are called CD-R recorders,and the process is a chemical one, "burning" the data onto a CD "gold master." CD gold mastersare also called "one-offs" because they are not used for mass production. If more than a fewcopies are needed, the bulk copies are made at a manufacturing site using the gold master to makea glass master from which production copies are made. Making a glass master is a physicalprocess rather than a chemical one, where the data are "stamped" on the disc. Only a few largefacilities have the capability of mass producing CD-ROMs.
**MANAGEMENT ISSUES**
A primary management issue concerns responsibilities. Who is responsible for development of aproduction capacity? Who is responsible for production once the capacity is established? TheProduct Development Plan, discussed in a later section, calls for a product manager who has theprimary responsibility for executing the Plan. This is the first time in NGS that a product has adesignated "manager." The team recommended that one of the authors of this paper, WilliamWallace, be the product manager. During the development phase, the Systems DevelopmentBranch of NGS will support the product manager to develop a productive capacity by executingADP procurements, assisting with data base retrievals, and developing software. Once aproductive capacity has been reached, the National Geodetic Information Center (NGIC) will takeover routine parts of the production process and sell and market these products. It is importantthat NGS understands the impact of this product upon our existing clientele and identifies newclientele as well as their additional needs.
Another management issue concerns the budget for this project. How much funding and howmany personnel will be required for development and then steady state operations? Based ondiscussions held with others in NOAA who have had extensive experience with CD-ROM,notably the National Oceanographic Data Center (NODC) and the National Geophysical DataCenter (NGDC), the team learned that costs could be well defined before the fact. The cost ofdesktop premastering and mastering hardware and software, i.e., for making the gold masters,was described in the previous section to be in the  $5,000 to $8,000 range at the time of thiswriting. This has come down considerably in the past couple of years and may continue to do so.The time it takes to do the mastering depends upon several factors such as the size andcomplexity of the data files, and whether search and retrieval software is to be included. Ingeneral, this process will involve one person's time for about 4 to 8 hours, depending uponcomplexity. The cost of mass producing copies at a manufacturing site will be in the $2 to $5range per copy, depending upon graphics required for the label and jewel case, number of colorsneeded, etc. 
Some other questions for which answers are less well-defined concern decision points. Whatresponse from users is expected? What is the minimum response at which this can be considered aviable product? Conversely, under what conditions might it be dropped? Some of the answers tothese will be based upon past experience with  existing products and NGS' traditional users. Thisleads us to topics covered in the next section.
**DISTRIBUTION ISSUES**
These issues are concerned with topics such as the projected market for the CD-ROM product,pricing of the product, and marketing plans and strategies. The NGIC of NGS has over 20 yearsexperience with providing established products to our customers. The current customer mailinglist contains approximately 4,500 addresses. Most of these fall in the category of "traditional"users of geodetic data, e. g., surveying and engineering companies and government agencieswhich require accurate positioning for their daily operations. The size of the typical company onour mailing list is in the range of 3 to 10 employees. Many small organizations are slow to investin new technologies compared with, for example, a government agency, due to limited resourcesto purchase state-of-the-art equipment. We saw this with Global Positioning System (GPS)technology during the late 1980s. Although many government agencies and large firms werebuying GPS receivers, most smaller companies could not afford the equipment until the pricescame down substantially. Such should not be the case with using CD-ROM technology. CD-ROMreaders can be purchased for as little as $200 to $500. This is a small amount when one considerswhat may be the cost of not using this technology.
The current data sheet product was described previously as being one county's worth of data ondiskette. The price of this is $30. When we did a preliminary pricing study for the CD-ROMproduct, we assumed an average production run of 500 CD-ROMs for each region. Whenproduction and distribution costs were computed, the cost we determined for the CD-ROMproduct was $50. If a customer only needs one county of data, he/she may opt for data sheets ondiskette. However, if much more than that is needed, it should be obvious that the CD-ROMproduct will cost less, even factoring in the cost of a CD-ROM reader. For example, if you wantdata for the state of Wisconsin on diskette the cost would be $2,160 (72 counties x $30). TheCD-ROM containing Wisconsin and twelve other states is $50. Because of this huge priceadvantage for those who need larger data sets, the team felt that CD-ROM would be welcomedby our traditional users.
How about potential users other than our "traditional" users? The rapid growth and usage of bothGPS and Geographic Information Systems (GIS) technologies has led to more interest and use ofNGRS data including the data sheet format. Since the NGRS is the most accurate nationwidecoordinate system, it serves well as the "base layer" to tie position-related information together ina GIS. Many NGRS stations are also GPS stations and are useful in geodetic applications of GPS.We are trying now to devise marketing strategies which will inform new audiences about theapplications of NGRS data and the CD-ROM product. 
At the end of the last section, there were questions about decision points. What would beconsidered a desirable response from users of the CD-ROM product? One suggestion is to seehow this compares to the number of requests we receive for the digital data sheets on diskette. Ifthe volume of requests for the CD-ROMs approaches the volume for the established product, wewould consider it successful. There will be information about this in the concluding section.
**PRODUCT DEVELOPMENT PLAN**
This plan was developed because the team believes that new products require a plan that definesthe product and assigns responsibilities. The definition is necessary so all parts of the organizationcan understand the product. The assignment of responsibilities allows different parts of theorganization to participate in the creation of the product. It also establishes common expectationsabout the time line for product development. Product definition and responsibilities have beendiscussed earlier in this paper. Here we discuss the production schedule, what it will take for aproductive capacity, and some auxiliary and possible future products.
The production schedule was determined by trying to realistically estimate steps on the time line.During the period when the team was still meeting, data retrievals were started for the NorthCentral region. This region was picked first because the massive flooding that occurred in theupper Mississippi River Valley during 1993 destroyed considerable geodetic control as well asboundary markers. During the summer and fall of 1993 NGS received more than the averagenumber of requests for data in this region. It took nearly 3 weeks to retrieve data for the 13 statesin the region without adversely impacting other computer-related activities at NGS. To beconservative, we would allow at least a month for this for other regions in case there are problemswith the retrievals.
Premastering and mastering for the gold master can be done in a day or less if there are noproblems. The team has recommended that NGS purchase the necessary equipment to do this.However, since any government procurement takes time, we have made arrangements withNGDC in Boulder, Colorado, to do this until we have our own capability. We decided to FTP(File Transfer Protocol) the data to Boulder over Internet and also send them an exobyte tape as abackup. The mastering equipment at their site is kept extremely busy, so we have to prescheduleour mastering several weeks ahead of time. After NGDC has made the gold master successfully,they send it by overnight mail to NGS. Again to be conservative we allow at least a week for thisstep. Graphics work for the CD-ROM label and jewel case inserts can be done while these firsttwo steps are being completed.
Finally, the last step is sending the gold master and graphics work to a disc manufacturing site forthe production of 500 copies of the CD-ROM. Most facilities will turn this around in 5 to 10working days. Combining these steps comes to approximately 7 weeks. For the five regions to becompleted in a yearly cycle, we can stagger their release by 2 to 3 months with some safety factor.The production schedule for the first year's volumes of the CD-ROM is as follows:RegionRelease DateNorth Central10/31/93Northeast12/31/93Southeast02/28/94South Central04/30/94West07/31/94
As of March 31, 1994 the first two CD-ROMs have been issued and the third is in production.New issues of the CD-ROMs with the most recent data will be done on a yearly basis on theanniversary of the original release date. Because geodetic data are subject to change, for examplewhen new surveys are added or existing data readjusted, we have to have some provision forupdating information contained on a CD-ROM before a new CD-ROM is made each year. SinceCD-ROMs are read-only, updates would have to be done on a separate product. Changes wouldmost likely not affect a large percentage of the data on a CD-ROM, so they may be provided onseparate high density diskettes.
To have in-house productive capacity for this CD-ROM product will require purchasing thenecessary desktop mastering hardware and software and a dedicated PC with at least a 1 gigabytehard drive (approximately $10K to $12K total). Manufacturing 500 copies at a service bureau willcost about $2,500 for each region, or about $12,500 each year. Staffing estimates for dataretrievals, graphics, any software needed, and product management are a total of about 0.5 staffyears per year.
Future additions to a CD-ROM product may include more sophisticated presentation softwarewith graphics capability. There are several software packages which are being tested whichcombine in-house written data extraction software with commercially available packages such asCAD. Putting geodetic computation  software and/or publications on CD-ROM is anotherpossibility. NGS will canvass its customers to see what types of products are most needed andpracticable.
**CONCLUSION**
The first year's five volume issue of geodetic data sheets on CD-ROM is considered by the PATto be a prototype product. There will almost certainly be suggestions and recommendations fromusers to add items or otherwise improve the product. The first volume issued, the North Centralregion, was initially sent to our state geodetic advisors. There are currently 26 advisors covering27 states (California and Alaska share an advisor). These advisors work closely with surveyors,engineers, and others within a state to coordinate and help with geodetic activities. Because ofthis, they are more in touch with users at the local level than most office employees at NGS, andare in a good position to test new products. Their reaction to the CD-ROM product has beenalmost universally positive. Many of them do not yet have their own CD-ROM reader, but allintend to get one as their state becomes available on CD-ROM.
After the initial positive response from the state advisors, NGS began to actively promote theCD-ROM product to its customers. Sales were slow for the first couple of months untilinformation flyers and advertisements were in circulation. Customer reaction, like the stateadvisors, was very positive. Most who did not already have the capability to read CD-ROMs saidthey would purchase readers in the near future. At the time this paper is being written (March1994), NGS has disseminated nearly 50 percent of its inventory of 1,000 CD-ROMs (500 eachfrom the North Central and Northeast regions). Since most customers are already familiar withthe data sheet product on diskette, they adapted easily to the product on CD-ROM. When wequestion users about what they would like to see added or changed, the most frequent response issome form of viewing software where data could be seen against a map base. Historically, NGShad a paper product called a "geodetic control diagram" which gave this type of presentation on amap base. Since we no longer support this paper product, we had anticipated a high interest insome graphic presentation of our digital products.
The answer to the question "Is CD-ROM a suitable and practical medium for large geodetic datasets?" is a definite "yes!" In fact, we predict that CD-ROM will replace most, but not all, of thedemand for digital data on magnetic tape. As CD-ROM readers become more commonaccessories for PCs, we may also see CD-ROM replace most of the demand for geodetic data ondiskette. However, NGS will continue to support all of these media as long as there is a need.
The team agreed that for at least the first two cycles of this product (2 years), NGS shouldcontinue to question customers about its suitability and the need for improvement. The willingnessof the customer to pay more for an enhanced product should be explored. We will also ask whatadditional products they would like to see on CD-ROM.
**ACKNOWLEDGEMENTS**
We would like to recognize other members of the PAT whose work contributed to this effort.They are Dr. Charles R. Schwarz (team leader), Vicki L. Davis, David R. Doyle, John G. Gergen,Dixon Hoyle, John D. Love, and Gary M. Young. We would also like to thank Craig B.Larrimore of NGS, the author of the digital data sheet software, for his help with data retrievals,and  David A. Hastings of NGDC for his assistance in making the gold masters for the first issueof the CD-ROM product.