Effective 15 October 2009 withVersion 2.09 Professional, DigitalAtmosphere now includes the LiveChart Retriever module. This is aprocess which streams live chartsto the printer, allowing weathercharts from NWS, NCEP, CMC,Met Office, or any weather agencyto be printed almost instantlywhen a graphic update occurs onthe server. This is designed toemulate the DIFAX and AFDIGSservice that existed from the 1970sthrough the 1990s, givingforecasters easy, immediate accessto paper products for handanalysis purposes. Charts areautomatically printed in fullresolution without the tedious,troublesome work that is requiredin Internet browsers.

It augments Digital Atmosphere’s own analysiscapabilities by providing a feature of great use tooperational forecasters. The Live Chart Retriever isalso similar to our Weatherpipe program except thatthe module actively checks for updates rather thanrelying on schedules, and it offers printer profilesand built-in image rotation. Weatherpipe will also beretired so that we can more actively focus on theLive Chart Retriever as an integral part of DigitalAtmosphere.

Concept of operationThe Live Chart Retriever is found in the Digital

Atmosphere “File” menu. This brings up theretriever control panel (Figure 2). Desired charts tobe printed are checkmarked in the Live ChartRetriever panel’s Chart Selection Menu. Once theretriever is activated, Digital Atmosphere examineseach chosen product and polls the server every 120seconds, using a HTTP HEAD request to ask theserver if the file has been updated. If the file on theserver is newer than the last one that DigitalAtmosphere encountered, it commences with a fulldownload. It is then sent to the printer.

Live Chart Retriever supports the use of multipleprinter profiles for each product. Though this can

Digital Atmosphere Professional V2.09 (15 October 2009)

Live Chart Retriever

Figure 1. Live Chart Retriever streaming automatically on ourinhouse Epson 1520 printer.

Figure 2. The Live Chart Retriever panel.

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obviously be used to send different kinds of charts todifferent printers, it can also be used to supportmultiple configurations of one printer.

For example, the Epson 1520 works with fanfoldcomputer paper. It is easy to select a paper heightmuch greater than the distance between fanfolds,allowing giant images to be printed across folds.However the Epson 1520 does not allow formfeeds tobe turned off, so smaller images which normallyoccupy a much smaller print space will be followed bymany inches of wasted paper when the printerinitiates a form feed. By associating most graphicsto smaller paper size profiles except for the giantimages, it is possible to reduce paper waste ontractor feed printers.

Live chart retriever controlsThe following list summarizes the features and

options available on the main retriever panel (Figure2).

* Dog icon. A green box around the dog iconconfirms that the retriever is active. A red boxindicates that it is inactive. An orange box indicatesthat a user-defined time suspension is in effect.

* Activate retriever engine. When toggled on, the

Live Chart Retriever will monitor the Internetproducts which have been checkmarked in the chartselection menu. The dog icon will have a green boxto show that it is active. When the retriever isturned off, the dog icon will have a red box to showthat it is off.

* Disable between (hours). If checked, this forcesthe retriever to suspend its activities daily betweencertain hours. The UTC time is used. This settingis useful if a forecast office is closed and no chartsare needed during those times. Each time must beentered in four-digit hhmm format, e.g. 2115 for21:15 UTC. If the end time is smaller than thestarting time it is correctly assumed that thesuspension is released at the given time on thefollowing day.

* Status message. A status message is displayedjust below the “activate retriever engine” control.This shows what the retriever is currently doing.

* Chart selection menu. This button causes theLive Chart Retriever chart selection menu (seeabove) to be displayed. See the next section for adescription of this menu.

* Close. When pressed, the Live Chart Retrieverpanel is dismissed. If the retriever is active, it will

Figure 3. The Chart Selection Menu.

still continue to monitor and download charts.

* Printer profile number. This control is used toview any desired printer profile. The profile “0” isthe default profile. Use the “up” and “down”controls to see a different one. The printer assignedto that profile will be displayed to the right of theEdit button.

* Edit (profile). Press this to edit the details of thedisplayed profile number. This will cause a printerconfiguration panel to be displayed. If theconfiguration is exited with “Ok” that printer settingwill be assigned to the profile number shown.

* Startup behavior dropdown box. There is adropdown box that dictates how the Live ChartRetriever will behave when it is started. If theretriever has not been run in days, then there is thepotential for all chosen charts to be downloaded andprinted, which may not be wanted. Possible choicesare “Do not print any charts on startup”, “Printonly missed charts on startup”, and “Force print allscheduled charts”. The preferred setting must bechosen before the retriever is activated.

* Rotate printer output 180 degrees. If it ispreferred that the charts come out of the printerrotated 180 degrees, then check this box.

* Disable printing. To test the retriever withoutprinting anything, check this box. Attempts to printwill be indicated in the engine status.

* Products queued for polling. Products willappear in here about every 2 minutes. DigitalAtmosphere has been instructed to check with theserver whether newer versions are available.

* Retriever engine status. This window showswhat the live retriever is doing.

* Preview of last downloaded product. Thiswindow confirms the appearance of the lastdownloaded product to show what the Live Retrieverobtained.

Chart selection menuThe chart selection menu (Figure 3) is a listing

of numerous Internet charts which can be activated.There are about 100 charts that ship with DigitalAtmosphere but many more can be added, allowingfor soundings, cross-sections, and other chartsavailable on the Internet to be printed whenavailable.

A checkmark indicates that the product is active.

If the retriever engine is active, then active productswill be monitored on the host server. Items withoutcheckmarks are inactive.

To sort the columns, click on the columnheading.

To delete a product, press the DELETE key onany line. The item will be permanently removed.

To add a new product, press INSERT to insert anew product. Type in the product, using theproducts above and below and the informationcontained in Table 1, Chart Selection Menu, as aguide.

LimitationsLive Chart Retriever is limited to these image

formats: JPG/JPEG, GIF, PNG, and TIF/TIFF(CCITT Group 4 only). The former three constitutethe vast majority of Internet images, while the latterone (TIF) is provided for compatibility with NCEPand WMO chart transmission standards. AnimatedGIFs are not supported. Requests for other formatscan be submitted to us for consideration.

Currently there is no support for passwordprotected files. We may add this in an upgrade, butwork on it is not planned since we expect that thevast majority of users will be using graphics that arefreely available on the web.

Chart Retriever does not support non-HTTPInternet protocols, such as FTP, HTTPS, SSL, orTelnet.

The live retriever will use any proxy usernameand password settings found in the DigitalAtmosphere File > Preferences panel. Proxy supportis provided as-is and we cannot troubleshoot issueswith it.

Usage of TIFF filesDue to a shortfall in available components,

Digital Atmosphere does not currently support TIFFformat natively. Users who wish to access TIFFs(especially for NCEP DIFAX products) must installfour files that are part of the Libtiff Win32 package:fax2png.exe, libtiff3.dll, libpng13.dll, andjpeg62.dll, and place them in the same folder whereDigital Atmosphere executable (digatmos.exe)resides. When this is done then TIFF support will beenabled.

We do not distribute these files because they fallunder the GNU General Public License whichprohibits them being packaged with commercialsoftware.

You may obtain the four files at:http://www.weathergraphics.com/dl/fax2png.zip

Simply unzip to the same directory where the

Table 1. Chart Selection Menu elements.The following table lists the elements of the chart selectionmenu.

product - Plain language name of the product. This may be setto whatever the user likes. It is not used by the software.

origin - Origin of the product, strictly for organizationalpurposes and is not used by the software. The abbreviationswe are using include:

DIFAX NCEP products that are part of the DIFAX familyCPC NCEP Climate Prediction CenterNCEP Other NCEP productsGEM CMC GEM productsCMC Other CMC products

level - Level of the product, strictly for organizational purposesand is not used by the software. We use H500, H700, H850,etc for the mandatory levels, FL180, FL300, etc for flightlevels, SFC for surface, and XXX for nonspecific levels.

VT hour - Forecast valid time in hours. This is strictly fororganizational purposes and is not used by the software. Thisshould always be in 3-digit format otherwise sorting willcause rows to be sorted as 0,12,120,24... instead of000,012,024,120...

area - Geographical area, strictly for organizational purposesand not used by the software. Our convention is as follows:

US United StatesNA North America (we recommend not using “NAM”)NH Northern HemisphereATL Atlantic Ocean basinPAC Pacific Ocean basinIND Indian Ocean basin-E Suffix for east-W Suffix for west-N Suffix for north-S Suffix for south-T Suffix for tropics

rotation - If charts come in upside down or sideways and youdo not wish them to be printed that way, you may force arotation after download by putting in a value of 90, 180, or 270.Sideways graphics that are to be printed sideways should beleft at 0.

profile - The number here indicates the printer profile numberthat should be associated with this chart. It should normallybe set to 0 unless you want it associated with a differentprinter profile. If that printer profile does not exist, the chartwill be printed with profile 0.

URL - URL of the resource. This must be a direct link to animage. Acceptable image formats are JPG, JPEG, GIF, PNG,TIF, or TIFF (TIF/TIFFs must be CCITT Group 4 only). A link toan HTM, PHP, or other page will not work!

Digital Atmosphere executable resides (and if youaren’t sure, right click the Digital Atmospherestartup icon and select Properties).

In a coming release, we will provide nativesupport and eliminate this requirement.

Printer considerationsOne often overlooked consideration is the

suitability of letter-sized printers to meteorologywork, a task that is heavily map-oriented. Userswho do extensive analysis and forecasting shouldgive consideration to whether their printer isadequate for the job.

The optimum printer for the forecast desk is theso-called “large format” printer. This type of printerhandles the so-called ledger or tabloid paper sizes,which are 11 x 17” in the U.S. and A3internationally. Inkjet offers the lowest cost, and asof 2009 street prices of these printers were about$400 new. Printing should always be done on plainbond paper, not photo paper (which tends to be theselling point of large format printers). Many of theseprinters accept tractor feed (e.g. fanfold paper, alsoknown as “computer paper”), which can actually bequite cheap, is less prone to jamming, and allows forvariable map sizes. The cost of consumables can bedrastically reduced if weather charts with whitebackgrounds are used, such as those available fromNCEP and the legacy DIFAX charts. These allow forvery low ink consumption.

Some large format models to consider include theHP Photosmart Pro B9180, the Epson R1900, andCanon Pixma Pro 9000. However those are just afew examples and many other models exist. Duringmuch of the late 1990s and early 2000s, theworkhorse printer of choice was the Epson 1520. Itis out of production but can still be found used forabout $100-200, and cartridges are still beingmanufactured.

Industrial users may consider “wide format”printers, which have a width of greater than 17inches and a cost of over $1000. However such sizesare really not necessary since ultra-high weatherchart resolutions are rarely encountered.

Technical supportRegistered users may obtain support by

contacting servicedesk@weathergraphics.com .

- TIM VASQUEZ / 10/15/09