GND CONFLICT OCCURS DURING A RWY INCURSION BY A TAXIING C206H LAW ENFORCEMENT ACFT MAINTAINING COM WITH THEIR GND UNIT AT A SURVEILLANCE SITE NEAR ARPT.

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I WAS TAXIING A C206H AT ZZZ. I WAS ON A LAW ENFORCEMENT MISSION AND WAS ACCOMPANIED BY AN OBSERVER/CAMERA OPERATOR WHO WAS SITTING IN THE REAR OF ACFT. OUR MISSION WAS TO CONDUCT AERIAL SURVEILLANCE IN CONJUNCTION WITH SEVERAL GND UNITS. PRIOR TO OUR DEP; THE GND UNITS HAD CALLED SEVERAL TIMES REQUESTING OUR ETA AND TO EXPEDITE OUR ARR ON STATION. AFTER ENG START AT RAMP; I REQUESTED CLRNC AND TAXI INSTRUCTIONS THROUGH ZZZ GND. I WAS INSTRUCTED TO TAXI TO RWY 18R VIA TXWY B; HOLD SHORT OF RWY 36L AND RWY 9. I UNDERSTOOD AND READ BACK MY CLRNC AND PROCEEDED TO TAXI. I WAS THEN CLRED TO CROSS RWY 36L AND HOLD SHORT AT RWY 9. I AGAIN UNDERSTOOD AND READ BACK MY CLRNC. AFTER XING RWY 36L AND TURNING ON TXWY B; OUR GND UNITS AGAIN REQUESTED OUR ETA AND WERE ADVISING US OF THE STATUS OF THE SURVEILLANCE. AT THIS POINT I REMEMBER TURNING AROUND AND INSTRUCTING THE OBSERVER TO INFORM THEM WE WERE ON OUR WAY. IT WAS AT THIS TIME I REALIZED I WAS XING RWY 9 AND I SAW A SINGLE ENG CESSNA CONDUCTING A GAR AND PASSING SEVERAL HUNDRED FT ABOVE MY ACFT. I HAVE BEEN OPERATING AT ZZZ APPROX 7 YRS AND AM VERY FAMILIAR WITH THE RWYS; TXWYS; HOLD SHORT LINES AND WITH GND AND TWR INSTRUCTIONS. I FEEL ZZZ GND'S INSTRUCTIONS WERE VERY CLR AND CONCISE. MY EXPERIENCE WITH ATC AT ZZZ ARPT AS WELL AS ZZZ APCH HAS ALWAYS BEEN VERY POSITIVE AND THEIR PROFESSIONALISM; PROFICIENCY AND COURTEOUSNESS HAS ALWAYS BEEN GREATLY APPRECIATED. I HAVE APPROX 4000 HRS FLT TIME IN HELIS; SINGLE AND MULTI-ENG AIRPLANES. I HAVE BEEN VERY FORTUNATE TO HAVE NEVER BEEN INVOLVED IN ANY TYPE INCIDENT. IN FACT; I THINK THIS IS THE FIRST TIME I HAVE ACTUALLY CROSSED A RWY (ACTIVE OR INACTIVE) WITHOUT LOOKING BOTH WAYS. I AM CONVINCED THAT THIS INCIDENT WAS CAUSED BY ME ALLOWING DISTRS WITH THE MISSION TO ENTER THE COCKPIT. THIS HAS BEEN A LESSON LEARNED FOR ME. NEVER ALLOW MISSION ACCOMPLISHMENT TO RUSH AN DISTRACT YOU WHILE TAXIING OR FLYING; NO MATTER HOW ROUTINE THIS TASK CAN BE THOUGHT TO BE. ADDITIONALLY MY FOCUS CANNOT BE ALLOWED TO BE DIVERTED TO ANYTHING BUT THE SAFE OP OF THE ACFT I AM OPERATING.