Single engine pilot on a ground patrol inspection flight reported a NMAC while transitioning near a non-towered airport. The pilot reported encountering a non-communicating aircraft as the pilot flew across the runway center line a fair distance from the airport. The patrol pilot reported making all the appropriate calls near the airport. The other pilot only called turning final then ask the patrol pilot why are you there. The conflicting aircraft was non ADS-B.

Narrative

I was conducting aerial pipeline patrol activities near the ZZZ. My route brought me into the area from the south; with an initial eastbound turn towards the refinery/power plant at the XXX degree radial 5.5 NM fix from the ZZZ airport. At approximately 5 miles east of the airport; I began a 180 degree turn and proceeded westbound on an approximate XXX1 degree heading following a pipeline for visual inspection. This pipeline runs east/west just south of the ZZZ airport approximately 4000 ft. off of the approach end of Runway XX. During this time; I made multiple traffic calls on the ZZZ airport CTAF frequency broadcasting my intentions; position; and intended position; as well as coordinated with other aircraft in the traffic pattern at the ZZZ airport to ensure positive separation. As I was westbound and directly south of the airport crossing the XX extended centerline; I see what appears to be an experimental bi-wing aircraft at my 12 becoming 11 o'clock position at the same altitude or slightly above me. Due to the glare of the sun; I was unable to see this aircraft prior to this position. This aircraft; whom the pilot only referred to as 'experimental;' began to make a left turn to join a tight base for Runway XX. While in the turn; the pilot made a radio call 'ZZZ traffic experimental turning base XX.' No other radio calls for this lap in the pattern by this pilot were made. I asked the pilot if he has visual contact on my aircraft to which he said 'negative.' I informed the pilot he is turning into me and to maintain his present heading as I started a climb. Despite my broadcast; the pilot of the experimental aircraft continued to make a left base-to-final turn; and asked where I was again. At this point I told him I'm directly off of his left; as he was still in his turn to final to which the pilot asked 'I don't know what you're doing there anyway;' despite multiple traffic calls made by myself announcing my intentions and position. After a slight climb and turn to the left; I determined that the traffic was no longer a factor and continued on my route. The pilot of the experimental aircraft; while in the downwind phase of his traffic pattern; would have been to my right; giving him the right of way. However; due to his lack of radio calls; not operating with ADS-B out; and the position of the sun creating a glare making me unable to visually see him while in his downwind made it nearly impossible for me to know he was there. These factors combined with him continuing in a turn; despite my notification of my position to him and request for him to maintain his present heading resulted in a loss of separation that I would estimate between 300 [to] 500 ft. laterally and 0 [to] 150 ft. vertically. The only other radio call I heard from this aircraft was his last lap in the pattern; giving me the visual picture that I was only working around one other plane in the traffic pattern; whom in which I was coordinating my position with and I was under the impression he conducted a full stop landing and was no longer a factor. I made no observation of any other radio call during any other phase of his traffic pattern and he was not visible to me during my scans for traffic until he was practically right in front of me. While there were many fast acting factors that resulted in a loss of what I would consider safe separation between two aircraft operating under visual flight rules; I personally believe the main factor was the experimental aircraft's pilot failing to make proper radio/traffic calls to ensure all aircraft operating within the area have a clear picture and maintenance of situational awareness.