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Text File | 1992-07-22 | 24KB | 408 lines

RADARSCAN V1.1 (c) 1992 Tim Vasquez I. INTRODUCTION. RadarScan! (Big fanfare, please). It's a command-line controlled program which plots high-resolution color radar maps from text files containing raw National Weather Service radar data. It's an excellent tool for pilots, amateur weather persons, storm spotters, storm chasers, and anyone who wants to have the upper hand on the Weather Channel! Overall, RadarScan produces charts that are strikingly similar to those disseminated over NAFAX circuits by the National Meteorological Center. But not only can it overlay echo features and heights. It can overlay customized geographical features such as highways and cities. It shows the status of ALL radar stations involved, which lets you know where coverage may be lacking. And since it's as fast as your data source, it can give you a map which is only 10 minutes old! Finally, RadarScan also does away with those warped "teletype"-style radar dot maps available on many databases. If you've used one of them, you know how difficult it is to locate a city accurately or plot straight-line routes. II. REQUIREMENTS. You need a PC with at least EGA (640 x 350 x 16) graphics. A 286 (AT) or higher grade computer is recommended for best processing speed. Finally, a source of radar data is required which does not modify the report (CompuServe, AccuWeather, etc). III. TERMS OF USE. This program is shareware! If you use it past 30 days, you are required to register. Like most other people, I use and register my shareware. But I know how irritating it is to register a program where the authors ask for $30, $40, even $50! Not me -- I think $10 is a fair price for us both. So send in your registration! The address? Tim Vasquez, 3222 Kingswood Drive, Garland, Texas 75040. In return, I'll mail you a 5 1/4" disk containing the full-blown version of the program. It features zooming, city and highway overlays, and optimization. Plus, you get expanded documentation which includes a guide to radar reports and severe thunderstorm structure. And even if the price goes up, you've already entitled yourself to free updates. It's EASY to update your registered copy! If I update the program, I'll update the "demo" on CompuServe. You should be able to find a copy in the AVSIG forum. All you have to do is download this file and unzip it in a temporary directory. Then simply copy RADAR.EXE file from it to your RadarScan directory. When you run the new program, RADARSCAN WILL RECOGNIZE THAT YOU ARE REGISTERED and will disable its demo mode. If you're not on CompuServe, you may send a blank disk and a self-addressed stamped envelope (disk mailer) to the above address to receive any updates. If you're on any BBSs, you have my blessing to upload and distribute this package freely. My only restrictions -- you may not tamper with the content of the RadarScan package in any way, nor can you sell the package for profit or include it as part of another package. If you have any comments, suggestions, or questions, you may direct them to the above address, or to CompuServe 71611,2267. IV. QUICK DEMONSTRATION. To see the demonstration data, change the current directory to that holding RadarScan. Then, enter: RADAR SAMPLE 1 The "1" is a parameter which indicates that you want to see data in the file "SAMPLE" for the hour of 01:00 UTC (or Zulu, Z, time). To convert UTC to Eastern Standard Time, subtract 5 hours). The program will then only examine reports for 01:20 to 01:40 UTC (roughly about 8:30 pm EST). When you are done looking at the map, hit a key. V. OPERATION. Here's what it takes to use RadarScan. Once you get familiar with the process, you can take advantage of the command-line parameter structure to build batch and script files which automates the entire process to your own specifications. And with the right software, you can even let your PC dial up a new radar map every hour -- automatically! A. ACCESS the data. Using any quality terminal communications program, log into your database and capture ALL radar reports in the United States for the hour. An entire hour's worth of radar reports usually takes about 10K of space and about 1 minute to receive at 2400 baud. On CompuServe, access data by entering GO AWX to go to the aviation weather menu. Type SD @ALL at the menu. On AccuWeather, the command is RADU * C. On other databases, consult the user's guide for accessing all reports. Radar reports are filed at about 35 minutes past the hour, so it is wise to postpone data access between the minutes of :25 and :40. Otherwise, you will get a mixed bag of old and new reports, and not as many reports will be plotted. B. CAPTURE the data. To do this, turn on your "capture" or "disk log" function to capture the raw radar reports. Make up any file name. If you prefer to let RadarScan choose the file, capture the data to RADAR.TXT in the RadarScan directory. You may prefer to use my own method. I enter the date for a filename, and the hour for the file extension. For example, if I get 22:35 UTC reports for June 8, 1992 (UTC date), I will enter 08JUN92.22Z as a filename. To clean up my directories, I can use DOS wildcard commands (for example, DEL ??JUN??.* gets rid of all June reports). If you are saving to an existing filename, make sure that it doesn't contain reports for the same hour from another day. This will confuse RadarScan, which has no way of telling the dates apart. The best policy is to have the capture command destroy the file if it exists. While the data comes across, note the time shown on the reports. This will make it easy to remember what UTC time to enter when running RadarScan. C. RUN RadarScan. Exit the telecommunications program, change the current directory to the RadarScan directory, and run RadarScan using command-line parameters as shown below. When the legend appears, you may invoke your system's screen-dump program to send the picture to the printer. In any case, hit any key to exit the program. Command structure (insert spaces between all groups): RADAR [file] time [/z(zoom)] [/a] [/c] [/h(height)] [/r] where file = Optional filename for the raw data. If no filename is specified, data will be accessed from RADAR.TXT. You may path out of the RadarScan directory to access the datafile (e.g. C:\DATA\14JUN92.04Z). time = Mandatory. Hour of the data in UTC (Z) time. If you are unsure, check the times of the reports manually. /z(zoom) = REGISTERED VERSION. Immediately after /z enter a radar station ID and a zoom size from 1-9 to center the map on that location. For example, /zokc5 zooms on Oklahoma City with a size of 5 (the larger, the wider the area). /a = Optional. When /a is selected, it accesses the alternate palette. This is helpful, for example, to get a different color set for your screen dump program. /c = Optional. REGISTERED VERSION. When selected, RadarScan overlays customized city locations onto zoomed images. /h(height)= Optional. REGISTERED VERSION. When selected, plots maximum tops, hail, hook echoes, BWERs, and LEWP locations. It does this on either the national map or zoomed maps. If a height is specified, only storm tops above that level will be plotted, along with all other features, which greatly reduces clutter. /r = Optional. REGISTERED VERSION. When selected, overlays customized geography patterns (highways, roads, airways, county lines, etc) onto the image. Only for zoomed images. VI. HOW RADARSCAN WORKS. RadarScan sifts through the U.S. weather radar network reports and squeezes out all possible data. Its main source of information is from MDR (manually digitized radar) code and polar-coordinate cell reports in the report (echo areas are not used since they often duplicate the MDR data). MDR data describes intensity levels within a 20-mile grid (variable with latitude) overlaid on the radar sweep area. Using MDR data, RadarScan builds the best possible image by painting a "base map" of light precipitation, then discretely painting higher intensities on top. Since high intensities usually cover a small region, the size of the pixels are drawn as a reduced size. The entire process does some time, but this is in order to produce the best map quality available. The FAA (Federal Aviation Administration) operates a network of long range air-traffic control radars across the western United States. RadarScan reads these reports, too. If heights are desired (and if the program is registered), RadarScan will then sort through the radar reports again. It will find significant cloud-top heights and plot these on top of the image. It also looks for important radar signatures such as hail, line-echo wave patterns (LEWPs, a dangerous squall-line pattern), bounded weak-echo regions (BWERS, also known as "vaults" which indicate tornadogenesis), and tornadic hook echoes. It plots the precise location of these features on top of the color map. VII. INTERPRETATION. Since a single, small radar echo can straddle a grid border, the MDR code may take more grid boxes than neccessary to define it. This makes radar echoes somewhat larger than they really are, an effect known as "blooming". Although radar operators try to reduce this, it is an inherent drawback of gridding radar echoes and may be reflected by RadarScan. Here are the elements of a radar chart: A. RADAR SITES. They are identified in RadarScan by a mark or an abbreviation, precisely centered on the radar site. It will appear as follows: * + -- The site is reporting echoes, which have been plotted. * NE -- PPINE, Plan Position Indicator No Echoes. The radar is not detecting any echoes. * NA -- PPINA, Plan Position Indicator Not Available. The radar is inoperative, but is not down due to maintenance. * OM -- PPIOM, Plan Position Indicator Out for Maintenance. * NS -- PPINS, Plan Position Indicator No Significant echoes. Echoes are very small (cover only 20% or less of the grid box) and do not exceed VIP 1. * DE -- PPIDE, Plan Position Indicator Duplicate Echo. Although the site is detecting echoes, a sister radar is reporting them, so no report will be made. Used by the FAA air traffic control centers where the meteorologist sees several radar displays at once. B. VIP LEVELS. All radars contain circuitry which shows the radar operator the intensity of different parts of the echo pattern. These have a direct relation to the amount of rainwater contained within the cloud. At high intensity levels, this implies that a strong convective process is occurring, which often means hail. However, the presence of hail means that less rainfall is occurring than otherwise might be indicated. RadarScan assigns different colors to different VIP (intensity) levels. ECHO RAINFALL RATE (inches/hour) TYPICAL VIP INTENSITY Stratiform Convective DESCRIPTION OF ECHO 1 Weak < 0.10 < 0.20 Light rain 2 Moderate 0.10-0.50 0.20-1.10 Healthy rain shower 3 Strong 0.50-1.00 1.10-2.20 Thunderstorm 4 Very Strong 2.20-4.50 Strong tstm, some hail 5 Intense 4.50-7.10 Severe tstm, hail 6 Extreme 7.10+ Severe tstm, hail 8 Distant Heavy 9 Distant Light C. ECHO TOPS. By tilting the radar antenna, the radar operator can construct a cross section of the thunderstorm on a special display. From this, the height of the storm can be determined. On raw reports and in RadarScan, echo tops are indicated in hundreds of feet MSL (above mean sea level). The tops have a direct relation to the amount of energy available to the storm, but this does not imply that the storm releases it destructively. For example, we might think a 70,000 foot storm would create death and destruction, but weak "popcorn" storms seen in the southern U.S. during the middle of summer sometimes reach these heights without any significant severe weather. As a general guide, this table will indicate the usual content of storms based on echo height. HEIGHT TYPICAL DESCRIPTION 20,000 Usually the minimum for a rainshower to become a thunderstorm 30,000 Normal height of summertime popcorn thunderstorms 40,000 Strong thunderstorm with heavy rain and isolated severe wx 50,000 Storm often contains hail, heavy rains, high wind 60,000 Normal height of springtime tornadic thunderstorms, Grt Plains VIII. CUSTOMIZING THE PROGRAM. With a little experimentation and effort, you can configure RadarScan for your own setup. Whether you run an amateur weather station, fly cross-country, or monitor weather for a company, RadarScan can be tailored to your specifications. A. GEOGRAPHY. (Registered users only). All geography can be modified by the user. There are two geography sets -- the North American "map" set, and the "road" set. Both are alike, and are both contained within the file RADAR.PLT. To get inside this file, use MS-DOS's EDIT command or any similar ASCII editor. Each row defines a point and represents the continuation of a line. When the latitude/longitude of -1 and -1 is reached, a new "map" line is plotted. When a latitude/longitude of -2 and -2 is reached, a new "road" line is plotted. The difference between a "map" and "road" set is that display of the "road" set is optional, based on whether /R is entered when the program is executed. The road set can also have a different color. For all entries, simply follow the layout of the existing data as a guide. B. CITIES. (Registered users only). All cities can be modified by the user, and are contained within RADAR.CTY. Use any ASCII editor such as MS-DOS EDIT to modify this file. The sample file included contains airfields and cities in Texas and Oklahoma. Delete or modify this file as much as you like, but do not eliminate it, otherwise you may have problems. The leftmost three columns contain the identifier of the city to be plotted. You can do like I do -- identify airfields by their standard three-letter code, and identify towns and cities by an arbitrary two-letter system. The city identifier is located in columns 1-3. The city name is located in columns 6-29 (for your own use only). Columns 30-31 contain the latitude in degrees, and columns 33-34 contain the latitude in minutes. Columns 36-38 contain the longitude in degrees, and columns 40-41 contain the longitude in minutes. If there are any unused columns, fill them with zeroes (i.e. write 79 degrees longitude as '079'). See the file itself for an example. C. RADAR SITES. If new stations appear in the U.S. radar network, the user can make corrections to add new stations. Stations can also be deleted. The radar sites are contained within RADAR.STN. Use any ASCII editor such as MS-DOS EDIT to modify this file. The three-digit identifier is contained in columns 1-3. This MUST be in uppercase and must match the exact identifier used in the radar reports. Columns 8-9 contain the latitude of the station in degrees. Columns 10-11 contain the latitude of the station in minutes. Columns 13-15 contain the longitude of the station in degrees. Columns 16-17 contain the longitude of the station in minutes. Fill any unused columns with zeroes (i.e. enter 82 degrees, 5 minutes longitude as 08205). D. COLORS. You don't like the colors? No problem. You can adjust them to your own tastes. All you need is a text editor. There are two files containing the palette -- these are RADAR.CO1 and RADAR.CO2. RADAR.CO1 is the primary file used by the program. When the /A option is selected, the alternate palette RADAR.CO2 is accessed. Both files are alike and can be edited with an ASCII text editor such as MS-DOS's EDIT command. Here is a breakdown of the file: ROW DESCRIPTION 1 Background color value (normally black, 0) 2 Color value for radar intensity level 1 (light precip) 3 Color value for radar intensity level 2 (moderate) 4 Color value for radar intensity level 3 (heavy) 5 Color value for radar intensity level 4 (very heavy) 6 Color value for radar intensity level 5 (intense) 7 Color value for radar intensity level 6 (extreme) 8 Color value for text (storm heights, features, etc) 9 Color value for radar intensity level 8 (distant heavy) 10 Color value for radar intensity level 9 (distant light) 11 Color value for "map" geography and radar status text 12 Color value for miscellaneous graphics (box borders, etc) 13 Color value for city/town/airport geography 14 Color value for "road" geography COLOR COLOR COLOR VALUE DESCRIPTION VALUE DESCRIPTION VALUE DESCRIPTION 0 Black 6 Brown 11 Light Cyan 1 Blue 7 Light Gray 12 Light Red 2 Green 8 Dark Gray 13 Light Magenta 3 Cyan 9 Light Blue 14 Yellow 4 Red 10 Light Green 15 White 5 Magenta IX. TROUBLESHOOTING. RadarScan contains many algorithms which are designed to catch human errors made by those disseminating the radar reports. While it succeeds in dodging most of them, you may find a few that slip through the cracks. So if you see an echo height of 90,000 feet or a hook echo over Idaho, you might want to browse through the raw text file using an ASCII editor (such as MS-DOS EDIT) and correct any deficiencies in the data that you see. Or, of course, you can just ignore it. Make sure that you have all RadarScan files residing within the same directory and that you CHANGE DIRECTORY to it before running RADAR. RadarScan will not run if called from another directory. Also, be sure that your data source does not "tamper" with the content of the raw reports. Even something as simple as stripping the equal signs (end of report markers) off the ends of the observations or adding extra characters will cause problems with the program. It would be nice if the program had pure "fuzzy logic" to handle these situations, but such is not the case. Fortunately, I haven't seen any data sources yet which do this. If you do encounter problems, contact me, or write yourself a utility which will preprocess the raw data. Finally, if you store, say, 1935Z data, ensure that there is no 1935Z data from another day. RadarScan cannot tell the two reports apart, and you may get some strange looking maps. You can avoid this by setting up your telecommunications program to destroy any existing capture file before opening one with the same name. X. PRECISION. Again, the image is only as accurate as the raw data and technical limitations of weather radar and of RadarScan's interpretation scheme. However, RadarScan uses precision in handling the data. All coordinates are transformed mathematically through the polar stereographic projection formula, so placement error is nominal and is subject to the precision of the data. The national MDR grid is based on the LFM-I grid used by National Meteorological Center supercomputers. I don't have their mathematical formula for translating Cartesian MDR coordinates to lat/long. I've tested some of my own formulas -- they come close but don't meet my standards of precision. Therefore, all echoes are vector-mapped from the radar site using MM as the center location without any gridbox offset. However, the vector direction is adjusted to account for the MDR-north declination across the United States. Overall, the maximum position error of all echoes relative to the real-world is subject to the limitations of the MDR grid (about 20 nautical miles), plus the deviation of vector-mapping instead of using a mathematical MDR grid (about 10 more miles). It is fairly accurate, and the method interestingly removes much of the "blockiness" from the map. Storm features, cloud tops, and so on are mapped exactly as transmitted -- vector coordinates from the radar site. Therefore, the error relative to the real world is about 1 nautical mile for this data, increasing slightly with distance due to azimuth fanning. Geographical boundaries, cities, and et cetera are mapped directly and mathematically and should contain no intrinsic error. XI. IN THE WORKS? Some ideas being considered for RadarScan updates include time-lapse animation and keystroke area movement. Another feature that might appear is automatic data-source dialing. Also, algorithms are being worked on which reduce processing time. XI. DISCLAIMER. THE RADARSCAN SYSTEM IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EXPRESSED OR IMPLIED. The author makes no claims or representation as to its accuracy, reliability, or fitness for a particular purpose. The author disavows any liability connected with the program and documentation. In other words, you use it at your own risk! If you want guaranteed precision and reliability, you may want to instead consider the thousand-dollar-plus packages produced for the weather industry. Although I will try to correct all errors and release updates, you should use the data with caution and common sense (especially for you pilots). Unformatted weather reports severely test the limitations of any processing method, and since this is a spare-time project for me, I haven't had the time to explore every last data string that could cause this program to malfunction. -- LIST OF UPDATES -- V1.0 7/04/92. Initial version. V1.1. 7/22/92. Eliminated processing of extraneous remarks from FAA ARTCC radar sites. Status boxes displayed at bottom of screen while program runs. Added user-defined ability to filter out low cloud tops when plotting storm heights. Slight documentation modifications.