The VATSIM environment makes radar identification all too easy for us. All the radar targets are generated by virtual pilots and hence the identification of each target is well known from the very beginning. In real world radar systems this is unfortunately not the case. When a radar target appears in the system for the first time it is just that, a spot on the screen. Such a target can be a primary target, i.e. a simple reflection of the radar beam off the airplane, or a secondary target, which means the airplane’s transponder has sent an active answer back to the radar antenna. This transponder signal may contain

  • Mode A: A four octal digit squawk code (0000 to 7777)
  • Mode C: In addition to the squawk code, the pressure altitude (read-out of an altimeter always set to 1013 hPa, respectively 29.92 inches of mercury)
  • Mode S: All that plus a 24-bit unique aircraft code and optionally the call sign of the aircraft

Associating that radar blip with an aircraft identification must either be done manually or automatically. And that requires special procedures, like having the pilot report his position, requesting him to squawk ident (a special signal of the transponder), or letting the airplane fly a turn to verify that this radar blip really is what the controller believes it is.

When a new flight comes into our airspace from an uncontrolled area, many of us are tempted to answer identified without having done all necessary steps to really identify that radar blip. It’s so tempting, because we see the aircraft’s identifier in the radar tag. It’s already there, so why do additional identification? Professional Radar Mode tries to simulate this additional complexity of aircraft identification by forgetting some of the data that EuroScope receives from the VATSIM servers.

Basic Elements of the Simulation

  • Radar stations: There is a new section in the ESE file. You can define where radar stations are located and the range where primary and secondary responses are visible for the radar. Also a linear slope can be added to raise the floor of the radar visibility in longer distances.
  • As Hungary is one of the testing areas of the S-mode receivers EuroScope treats S-mode aircraft differently from A+C-mode aircraft and can represent them by different symbols on the screen. Of course you can disable the S-mode features if it is not used in your area.
  • Radar holes: You can also define radar hole areas, where no radar responses can be seen, even though the aircraft is in range of a radar antenna. Those holes can for example simulate canyons and other areas with topographic conditions that make the reception of radar responses impossible.
  • Complete separation of the radar targets and the flight plans. They are maintained separately and will be correlated only when certain criteria are met. You can manually correlate and de-correlate the radar targets and the flight plans.
  • Flight plan tracks: All known flight plans are moved (just like hypothetical planes) if there are no correlated radar positions. You can define estimates for uncorrelated flight plan tracks. That way they are moved back/forward along their route.

There are already some improvements planned for future versions, so the current implementation is not what we expect to be the final state of professional mode.

How it is implemented


In the [[General Settings]] dialog you can configure several aspects of the Professional Radar Simulation mode:

  • Correlation mode: With this setting you can define how radar targets are correlated with the flight plans:
    • Easy VATSIM: This is the old method used by older EuroScope versions and all other radar clients available. In this mode, radar targets are always automatically correlated with their flight plans.
    • A+C-mode: Only the squawk code is used for correlation. A radar target is correlated with a flight plan only when the aircraft is squawking the assigned code and it is within correlation distance to its calculated position according to the flight plan.
    • S-mode: S-mode transponders transmit not only mode A+C signals, but also the call sign; so S-mode aircraft are correlated simply by matching the call sign; but this correlation still requires that the aircraft is within correlation range of the calculated position. S-mode correlation takes precedence over A-mode correlation, so an S-mode radar track for aircraft MAH123 will be correlated with the flight plan for MAH123 even if it is squawking a code assigned for some other aircraft.
  • Correlation distance: The maximum allowed distance between the radar position and calculated position according to the flight plan for a correlation to take place. If the distance is larger, no correlation will take place even if the aircraft is transmitting the correct call sign. Setting the value to 0 makes the correlation distance unlimited.
  • S-mode transponders: Unfortunately, there is no support for S-mode in VATSIM and most importantly in the pilot clients, so we must use some other information to simulate a mode-S transponder. EuroScope does this trick by using the equipment code in the flight plan’s remark section. Check the SB3/SB4 documentation about the codes. The default value of this field is IEFGRWQ, which means any aircraft using any of these letters in its equipment code will be regarded as mode-S equipped. That includes nearly all RNAV capable aircraft. To disable all mode-S features, simply clear this field.
  • Simulate radar coverage and outage: Check this box to enable radar position simulation according to the data from the ESE file.

After enabling the radar coverage simulation you may switch on and off the radar antennas individually. Check the .antennaoff and .antennaon commands at Command Line Reference.

Symbology dialog

This dialog is extended now. It contains an editor where you can draw your own symbols on the radar. Among others there are several symbols for the aircraft positions:

  • standby: It is used only in easy mode when you choose to show stand-by aircraft, too.
  • primary radar only: When a position is within the radar coverage area and the transponder is disabled.
  • A+C mode secondary radar only: When the position is within the radar coverage area and it is too far out to receive primary radar responses, but the transponder answers are detectable. When A+C-mode transponder answer is received this symbol is used.
  • S mode secondary radar only: Similar to the previous, but we receive an S-mode transponder response.
  • primary and A+C mode secondary: When both, primary radar position is received along with a A+C-mode transponder answer.
  • primary and S mode secondary: Same as before, but we receive an S-mode transponder response.
  • flight plan track: To display a position of an uncorrelated flight plan simulation.
  • coasting: When no radar position (neither primary nor secondary) is received for 30 seconds up to 1 minute. Whenever an aircraft is coasting within the last 10% of your visual range, after 1 minute the target is not deleted but changed to be a flight plan track, which is used the very same way as all the other flight plan tracks originating from statistical data.
  • ground aircraft: It is a new ground view, not related to the radar simulation.

Display settings dialog

This dialog is also extended with a Simulation mode combo:

  • Easy EuroScope mode: This is the original version. It works much more like the previous version of EuroScope. The positions are always shown at the radar position and do not care if they are correlated with a FP or not.
  • Professional radar: This is the real simulation mode. It can not be enabled if in the general settings you select Easy EuroScope correlation mode. It displays:
    • Flight plan tracks: for uncorrelated or no radar position aircraft. This is used for the far away (statistical data) traffic too.
    • Primary only radar: Just TSSR and GS without any identification method.
    • Secondary A+C or S mode: For secondary only positions.
    • Primary and secondary: When both are received.
    • Here there is no way to display stand-by aircraft like it was possible before.
  • Professional ground: This is a new radar screen. I tried to simulate what a controller can see from the tower. Here the symbol is always put to the radar position and it is rotated to follow the aircraft heading. In the TAG you can see the first three letter of the callsign (airline identifier – it can be visible from the painting) and the type of the aircraft. If you enable S-mode simulations then the planes on the ground can show their callsign too. In this mode you can not select anything on the screen. You must use the lists to manipulate the FP and the states.


The list of the TAG types is extended:

  • Untagged A+C-mode: This is the original untagged type. It is shown for primary + A+C-mode secondary radar positions. If the position is not correlated to a flight plan, then you are unable to tag it up.
  • Tagged: This is the original type, not too much change here.
  • Detailed: Also no change.
  • Primary only: The old Unidentified type. Used for primary only radar positions.
  • Untagged S-mode: This is a new version of untagged type. It shows the callsign instead of the squawk code due to the transponder answer.
  • FP track: This is a third type of untagged type. When showing a plane just by using its FP estimation, we can define some more information (like destination).
  • Ground: To show the airline and the plane type.
  • Ground with S-mode radar: To show the callsign with the plane type.

Whenever you select a TAG on the screen, the plane itself is selected. You can use the ASEL plane with many functions. In the new version, when an unidentified TAG is selected (primary only or uncorrelated radar TAG) then the plane itself is selected, but its data is not displayed. Nearly none of the functions will work with that kind of ASEL. One important exception is the .contactme command. It is sent to unidentified planes, too.

In case of an unidentified radar TAG you can only see the untagged version. There is no way to tag it up. The flight plan tracks can be tagged up, and even coordinated and be issued a or be accept as handoff. But it works only for those flight plan tracks that have real data behind from VATSIM. The flight plans that are outside your range and are only displayed from the statistical data can not be manipulated (even it is not easy to see the difference).

The ESE file extension

There is a complete new section in the ESE Files Description: [RADAR].

In this section you can define the radar stations and radar holes. The mode to define the radar areas are upgraded ti v3.2. Check the new radar antenna definitions.


When there is no radar response and a plane is displayed by the flight plan track only, you may enter some estimation when the plane will arrive to a certain waypoint. This is available as command line function, as TAG item and in the flightplan dialog. The command itself is the following:

.est <waypoint> <time> ASEL
.est <waypoint> <time> <click on AC>

  • waypoint: A waypoint along the route. It can be any waypoint, even one that was already passed. But only points along the route can be selected.
  • time: The zulu time in four letter format (e.g. 2235 for 22 hour 35 minutes). The time is limited. It must be in the future and maximum two hours later.