Part 107 government UAS pilot reported having a miscommunication with the FAA and the local control tower about the area of the UAS flight. There were no airborne conflicts and the flight was completed without issue.

Narrative

I received a radio call for a call for service. I was requested as a Drone Unit to search the surrounding fields. I knew that the location of this call was extremely close to the local International Airport which is surrounded by Class C airspace. I called the FAA number for SGI Emergency Waiver. I advised the FAA employee of my location and needs. The FAA Employee advised that he would call me back with a clearance. When the FAA Employee called me back with my SGI Authorization; I was given a 1/2 NM radius around the residence and 100 ft. ceiling for my clearance. I advised the FAA Employee that the Control Tower was calling my dispatch. The FAA Employee told me to contact tower and follow their instructions. I was advised I was clear to fly under the guidance of the air traffic controllers. I attempted to make contact with the Tower multiple times but was unable to. I called the FAA Employee back who gave me the number for regional approach/departure control. I called this number and spoke with a controller. The controller asked if there would be any interference with my drone. Knowing this area extremely well from flying actual fixed wing aircraft both IFR and VFR into this airport and with my knowledge of the city and where I was located; I did not believe there to be any potential conflicts with my drone. I advised the controller of this and he advised I was clear to fly and to call him when I landed. I advised I understood. For some reason based on my conversation with the controller; I believed I was cleared to fly where I needed and at whatever altitude I needed to for this mission. I proceeded to fly my mission. During this mission; I flew approximately .7NM away from the residence which was slightly father then I had received authorization for through SGI. I also flew to a maximum altitude of 170 ft. AGL which was 70 ft. above my SGI authorization. I called the approach/departure control again and spoke with the same controller. I am not entirely sure where the miscommunication came from; but it was likely that I was not specific enough when I called the SGI authorization number for clearance. The controller then advised I was again clear to fly and this time he specified that I was cleared up to 100 ft. AGL. It was at this time that I realized my error. I realized that the SGI authorization limits were still in effect; and I had busted the limits on my first flight. I had incorrectly believed that the air traffic controller had overwritten the original clearance; and I believed that I did not have an altitude or area limit when; in fact; I did. I accepted this clearance and proceeded to fly a second time. This time; I remained in the parameters original assigned to me. At no time did I come close to another aircraft during my first flight and no accident resulted. From this incident; I learned to not assume the parameters of my clearance and to clarify better. I also determined that I was in too much of a rush to get my drone in the air as a result I speed through the process as quickly as possible. I failed to be specific enough with both the FAA employee on the SGI hotline and with the Air traffic controller which resulted in some level of miscommunication. Finally; from now on I am going to assume that the parameters set by my SGI authorization are still in effect unless otherwise clarified. This was a good learning experience for any future flights I may have near the airport.