I recently started collecting position data and have been toying around with getting raw outputs. I am trying to add ground positions to the mix and notice that I currently do not get those positions. I saw in a separate discussion thread (FAdump1090 and traffic on ground) and saw obj’s response about needing to edit the init.d file.
I won’t pretend to know what I am talking about and come out and say I have no idea where to go to edit that file, or even how. I notice there is nothing like that in the sd card, and I have navigated to the usr/bin folder and noticed a file titled dump1090-fa, but no init.d file. I am wondering is this where I make my edits? Do I edit the dump1090-fa file directly? How?
That thread is very old, if you are running current dump1090-fa with piaware then it automatically picks up the receiver location from whatever you configure on your stats page.
Your receiver might be overloading if you are close to an airport (within a mile or less). You can try to lower the gain to about 20 and see if you get more ground positions. This is a trade off to seeing nearby ground positions and also long range positions.
I am noticing that I receive minimal surface position messages. I get a sufficient number of messages indicating speed and heading of ground aircraft, but not position. I understand that part of the problem could be lack of coverage with MLAT at the airfield, or alternatively could just be physically blocked view. Is there maybe a third reason that messages observed on port 30003 would not have position as often as airborne aircraft?
My site has serious attenuation (concrete buildings) between it and the airfield currently. That will change to direct LOS soon once I permanently mount my omni, but I am wondering if I need to also consider more antennae to boost MLAT.
I’ll also try tuning the gain down. The focus of this exercise is primarily tracking ground movements vs. long distance aircraft.
ADS-B surface positions are relatively infrequent (1 per 5 seconds) so it’s normal to see a lower frequency of position-carrying messages in the 30003 output. Note that 30003 roughly maps 1 line : 1 message on the air and doesn’t “coast” previous data so each non-position-carrying message will produce a line with no position.
Sorry, I should have mentioned I am also looking at data via port 8080 using aircraft.json. Will I see MLAT positions here, or do I need to read from port 30106?
i use dump1090-mutability and have tons of ‘ground’ messages in my database that aggregates the json-files. so i’d say the same should be default in dump1090-fa …
Ground positions are shown in Skyview when they are received by your site. Generally speaking, unless your antenna is on airport property or has line-of-sight to aircraft on the ground, you will not be able to receive ground positions from ADS-B aircraft.
