The 36th Survey Battery was a sound-ranging unit whose job was to pinpoint enemy guns so that the artillery could neutralise them. They did this from observation posts 2000 yards back from the enemy using recently-introduced sound ranging microphones set in drums. The microphones had a wire grid that was wired back to the equipment at headquarters. When the enemy guns fired, the observation post would press a button to start the unit recording sounds going through the grid. Shell waves and gun waves were recorded on the Headquarters machine. Allowance had to be made for the difference in meteorological air pressure and temperature.
Strength (11 May 1944): 13 Officers, 259 Other Ranks
36 NZ Survey Battery left New Zealand in February 1941 arriving in Maadi Camp, Egypt in March. For the next eighteen months, the Battery had a non-Divisional role, carrying out surveying duties in far flung localities. At various times the Battery had personnel in Egypt, Transjordan, Cyprus, Safaga (on the Red Sea coast of Upper Egypt), Aden and Syria. In December 1942 the Battery became a unit of 2 NZ Divisional Artillery, boosted in numbers by the addition of 1 Survey Troop. The composition of the Battery was then:
Except for R Troop, which was completing its training, the Battery joined the Division's conquest of Libya and the advance to Tunis (Dec 42 - May 43), playing its full part in the advance across North Africa.
Following the success in North Africa, the Battery returned to Maadi with the Division and prepared for the Italian campaign. When the Battery moved to Italy in November 1943, its strength was 284 all ranks. During the fighting in the Sangro-Orsogna region, six men from the Battery were wounded. The Battery continued its surveying, flash-spotting and sound-ranging throughout the Italian Campaign losing three dead. When 2 NZ Divisional Artillery was reorganised the Battery was disbanded (along with 14 Light Anti-Aircraft Regiment) in September 1944. One hundred and fifteen men went home, 67 were posted to other artillery units as reinforcements, and 25 were formed into 5 Survey Troop which became part of 7 Anti-tank Regiment. The Survey Troop was able to do ordinary surveying and fix bearing pickets but the tasks of flash-spotting and sound-ranging were done by outside survey regiments.
Throughout the Sangro fighting, 36 Survey Battery was very busy with flash-spotting and sound-ranging, operating well forward and with considerable success. The rate of sound-ranging locations was very high indeed and the flash-spotters were beginning to get good results from new flash-spotting cameras. In a letter to the CRA of 14 December, Major Drummond pointed out that checks on the ground of the accuracy of five locations shelled on information supplied by the Battery indicated that four were highly successful and the fifth, engaged on the basis of sound-ranging only, might have been successful had a flash-spotting location been taken into account. In addition to flash-spotting and sound-ranging the Battery was also very busy carrying out surveying and providing bearing pickets for the whole of the New Zealand Divisional Artillery.
Major Drummond actually left the Adriatic sector as early as 14 January with an advanced party, and on 16 January he consulted the artillery GSO III of the 5th Army at Caserta. From there he went on to Mignano to learn what he could from 2 American Observation Battalion. He camped there with his party for the night, near a regiment of 8-inch guns which as he noted 'made a lot of noise'. On the 17th the party had a look at American flash-spotting and sound-rangimg bases. The flash-spotting equipment was better than their own, but the sound-ranging recorder was of an older type.
The 36 Survey Battery flash-spotting base centred on Trocchio was manned for a total of 52 days and nights. Lance-Sergeant MA Keppell was in command of one OP at the southern end of this feature and he did not leave it once. It was shelled almost every day and on 29 March the enemy scored a direct hit, wounding two men and causing much damage to the equipment. Sergeant Keppell had the wounded attended to and then arranged for a reserve instrument to be brought forward. In a very short time the post was in full operation again.
In the Orsogna operations Sergeant Keppell had similarly kept a post in operation for 40 days. For this and his work on Trocchio he won an immediate MM. When the Battery withdrew to Venafro its record of flash-spotting and sound-ranging locations throughout the period of 52 days was excellent. Flash-spotting locations averaged seven per day and sound-ranging 7.4 per day. Moreover, they were to a considerable extent complementary rather than repetitive, since most flash-spotting locations were obtained when 5th Army guns were extremely active and no sound-ranging locations could be obtained, while most sound-ranging locations were of guns using flashless powder or in positions of good flash cover.
From Artillery Surveyors, 2NZEF, 1940-45, RD Munro, Feb 1994, and reproduced here with permission of the author.