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The basic facts which impinge upon the whole Diogo Homem storyline are necessary to avoid too much repetition of text. The chart from text ChRH/1/D01 is applicable here.

Diogo Homem was born c1515 in Portugal, was trained by his father Lopo Homem, completing c1535. He was in Portugal until 1543 when he was accused of murder and supposedly exiled to Africa. That did not happen and instead he escaped to London, obviously taking with him his pattern/templates as he was given a commission to produce a chart. That chart caused him problems in that it became the subject of a 1547 court case in the Admiralty Court London against the client.

He next appears in the records as preparing an atlas for Queen Mary of England, c1555. The intervening period from 1547 to 1555 is not on record. However whilst Diogo Homem is preparing the atlas, a Thomas Geminus prepared two large charts, one of Britannia and the other of Spain, obviously prepared to cash in on the forthcoming marriage of Queen Mary to King Philip of Spain, which was the purpose of the atlas. That chart of Britannia is a copy of the George Lily chart (see cg/EM/Gn/1 & cgEmO) and does not influence Diogo Homem, who as stated must have used his own Pattern/template and also possibly the now lost infamous 1547 chart. Thus we arrive at the beginnings of the extant works by Diogo Homem.


The extant charts and atlases are noted in date order on the two diagrams, with diagram ChDHa/1/D01 listing the 10 atlases to be examined and how their content compares to the Dresden Atlas of 1568. It indicates that the variety of charts within each atlas varies from 7 to 14 folios and what each folio contains varies considerably, which in turn indicates that the pattern/template was being manipulated for size, and thus scale continuously. That fact given the dating of the atlases can only lead to one conclusion, a prodigious work ethic and team.



However, only one chart folio within the atlases may be considered constant, that of the British Isles and the Atlantic coasts. They are of different scales and varying setting out and have been manipulated to equalize scales for comparison within this text. However the second atlas on the list, BNF Paris 1558, has a chart which covers the whole of Europe and Scandinavia south to Africa, and from the Cape Verde Isles to the Red Sea and Caspian Sea and is thus a miniature portolan chart. Two other folios in this atlas traverse eastwards to Vietnam.



This atlas page chart has both a scale bar and latitude scale from 35N to 60N and is actually more accurate than the latitude scale illustrates. That scale has the 36N latitude correctly positioned for the Strait of Gibraltar as well as the 37N to 43N latitudes for the west coast of Iberia. However the measurement from the scale bar is 70Sbu’s per degree. But, measure from the 36N geographical alignment to the 58N (northern Scotland) then the degree length apropos the Sbu’s becomes 73 units, which is close to the standard portolan measurement for the west coast of Iberia of 75 Sbu’s per degree, being the Roman Miles per degree, not miliaria of 90 per degree. The typical error of all portolan charts.

Longitudinally the majority of Iberia is a square chart and France becomes the same if the putative longitudes 3W to 3E are measured. However if the putative Zero Line of Longitude, drawn in Blue is measured the expansion of Iberia is clearly indicated and should be proportionally c56 Sbu’s per degree of longitude.

Where-as both Iberia and France are geographically well represented, the British Isles although clearly recognisable are drawn with Hibernia greatly exaggerated in latitude and Britannia itself given an easterly tilt instead of westerly.

Unfortunately as the c1547 chart the subject of the court case is no longer extant, then this atlas is in effect the primary source even though it is dated 1558 and using that date it becomes the third item on the list of Diogo Homem’s work, as ChDha/1/D02 illustrates, it must be borne in mind that it commenced life in 1555.



The atlas folio 3 mentioned previously as being a miniature portolan chart has obviously been reduced by possibly the use of a pantograph, along with the two other folios which would complete a world chart. If a comparison to the closest dated charts extant is made, it is obvious that neither the National Maritime Museum Venice chart nor the Volterra charts are the basis for the 1558 atlas. In fact the BNF folio 3 is actually c25% scale of the Queen Mary Atlas page discussed and given that a full chart is necessary to draw an atlas it would be quite in order to opine that the missing 1547 chart is the basis of these folios. The reduction by quantifiable amounts clearly indicates that fact.



This atlas chart of the British Isles, France and Northern Iberia has a scale bar 33% larger than the Queen Mary atlas, hence less is shown. But the latitudinal scale from 41N to 60N measures 66 Sbu’s per degree and the latitudes via the Geographical positions shows 14 degrees of 75 Sbu’s per degree, and as Roman Miles not miliaria is quite correct.

It is no doubt merely a scaled up version of the Queen Mary Atlas, however, it is obvious the latitudinal scale has been mis-drawn, evinced by the change in the alignments and the actual measurements. Longitudinally it would appear to be a square chart, which if it is a scaled up version of the Queen Mary Atlas is entirely correct. Visually they are identical which perhaps indicates that the scaling up is from the pattern/template used to draw that atlas.

NOTE; It must be clearly stated that the scaling up, if by a pantograph would not be by the use of a quill but by a blunt pointer making a small mark on the vellum acting as a guide for the freehand quill work. Thus there are no splodges of ink and neither are there splodges of ink if in fact a very thin charcoal was inserted to draw an actual line. The lines are too perfect and show no interference.



First seen in the BNF 1558 atlas, this atlas follows with a portolan chart of the Mediterranean Sea basin which is scaled 40% to the Queen Mary Atlas. The latitude scale measures 70 Sbu’s per degree. It is no doubt a magnificent Atlas page with the actual latitudes surprisingly good and actually scaling geographically 75 Sbu’s per degree with the corresponding longitudes at 66.667 Sbu’s per degree. The fact that the Flag of Venice is only outlined, where-as the Arms of the Holy Roman Empire are centred is perhaps the reason for its being incomplete. With the place name Lobardia, for Lombardy, capital Milan, indicating the Habsburg Dynasty when Venice was a Republic, which as Homem was ensconced there he would be very aware of the politics may also point to the recipient of the atlas.



Basically the same Atlas page as the BNF 1559 atlas (D05) with an average of 71 ½ Sbu’s per degree. But measured from the geography, 43N to 55N they are 78 Sbu’s per degree. I must state that due allowance has been made for the central distortion. This chart is c80% of the 1559 chart by scale bar measurement, but with the latitudinal centre line being similarly positioned.



This is virtually a direct copy of the 1559 chart and by scale bar is 94% size and I suspect are in fact meant to be identical. Both charts by geographical alignment are 75 Sbu’s per degree with the 1559 chart latitude scale being 66 Sbu’s and the LUL chart 70 Sbu’s per degree.
The decoration is a repeat and the English Arms are the Royal Standard of King Henry 8th and Henry 4th, between 1405 and 1603. They were then quartered and show France modern and England unfinished. For France, there are 3 fleur-de-lys in the 1st and 4th quarters and thus there should be 3 lions passant in the 2nd and 3rd quarters. This omission probably indicates the continental client base and the constant friction with England.


Yet another atlas page with a differing eastern limit and thus a smaller scale to accommodate virtually the 9E longitude through Corsica and Sardinia. The latitudinal scale bar is 66.667 Sbu’s per degree, but the geographical measurement from 36n to 58 ½ N is 73 Sbu’s. Longitudinally from 9W to 3E the scale is 63.33 Sbu’s per degree. These measurements are similar to the Queen Mary atlas which has nearly the same geography there-on.




This atlas page is very similar to the half folio of the Morgan Chart just discussed. However it is c166% larger, which is an easy scale to adjust to. Britannia Isle is drawn latitudinally at 75 Sbu’s per degree and the European coastline similarly drawn. South of 50N the latitudes are 90 Sbu’s which indicates the possibility that the Miliaria is at last being used correctly. Hibernia Isle is as usual drawn 166% larger latitudinally than Britannia, but longitudinally from Hibernia to Jutland, 20 degrees longitudinal they are 53 Sbu’s per degree.



This atlas chart is the Dresden chart extended southwards to the north coast of Iberia. It has two latitudes as per normal with the scale bar being 72 Sbu’s and the geographical being 80 Sbu’s per degree. Longitudinally it appears to be 50 Sbu’s per degree. It is in fact a curious chart in that it is drawn landscape format and thus wastes 33% of the page, being infilled with rather elaborate wind roses.


Possibly a direct copy of the Dresden chart being some 10% smaller. The latitudes are midway between 75 and 90 and could thus be either Roman Miles or Miliaria, but, both scale bar and geography agree at 82 Sbu’s per degree, with longitudes at c54 Sbu’s per degree.


It must be patently obvious that the scale bar drawing leaves much to be desired in accuracy. Given that they are quite short lengths and really only vary by small amounts it would not be correct to assume the variations that appear are in fact correct. The fact that the Latitudinal positions vary also, but the sizes of the Islands of Hibernia and Britannia are quite constant in comparative size shows a lack of accuracy was not considered important as these are in fact library works not to be used for sailing and thus it is doubtful the scales were ever used.


The latitudinal scale bar matches except for a small change north of the 50N latitude, but it is a consistent change from 50N to 60N. The overlay indicates just how similar these charts are given they are probably 10 years apart in construction. Thus I can opine that they are all drawn from the same pattern/template which is manipulated for scale changes to fit the folios requirements.



This has been included as it amply illustrates the basis of the Diogo Homem atlas, a square portolan chart based on latitudinal measures. The portolan chart is no different to those that precede it over the centuries, illustrating the anti-clockwise slew caused by the two latitude measures of 75RM and 90 miliaria being confused.



Within my text ChRH/1, I indicated a timeline for the Reinel and Homem families of cartographers as Diagram ChDHa/1/D02 showed. What it clearly indicated was that Diogo Homem after his fracas in Portugal arrived in London c1544/45 and produced or completed a chart which became the subject of an Admiralty Court case. But, after 1547 we lose documentary evidence of his whereabouts until he commenced to produce the Queen Mary Atlas c1555. Therefore from 1547 to 1555 where was he?
In 1554 Lopo Homem produced a world chart, now held in the Museo Galileo, Italy and Andreas Homem produced his world chart in 1559 in Antwerp and was in Paris c1560.

NOTE; I have now deliberately omitted the World Charts c1500 to 1530, mainly Spanish and basically the Padron Real and the charts now to be named are all illustrated in the Appendix for comparisons to be made and the obvious copying noted.

However Pierre Desceliers produced a World chart in 1550; ‘Faicte a Arques (La Bataille) par Pierre Desceliers PBRE; lan 1550.’ It is doubtful that either Lopo Homem or Andreas Homem knew of Desceliers and in fact it is fair to state that really nothing is known of him other than he was Presbyter in Arques La Bataille 1537-1553. But it appears he was a cartographer of a lost world map dated 1543 and we know of the 1550 map because it is held in the John Rylands Library, Manchester, and a chart dated 1553 destroyed by fire in Dresden 1915. Add to those, Jean Mallard, 1540, Jean Rotz 1542 and Guillaume Brouscan 1543, and there becomes a plethora of world Charts to be copied. To those we must add the 1529 chart by Girolamo de Verrazzano , brother of Giovanni Verrazzano the explorer and his famous letter dated 8/7/1524 to the King of France from Dieppe on his return.
The problem which has not been solved is that none of these other cartographer’s timelines and thus teachers has been identified to enable the progression to be set down.
With that in mind I have decided merely to discuss the Diogo Homem Atlas World Charts which can be found in the Queen Mary, Vienna Library and Dresden Library atlases.



ChDHa/1/D16 & 17

This chart is highly decorated as would be expected for a commission of such importance and has appended the names of countries throughout Europe, Asia and the Far East, with several also in the America’s. It is fairly representative of the known world c1530 and having interpolated the latitudinal and longitudinal degrees from the chart itself I can state that it is a square chart with in some sections a good accuracy. Being meant for a gift to King Philip of Spain the plethora of place names was no doubt incorporated because of his love of maps and the geography of the world. The setting down of each and every one would be a singular text alone!



ChDHa/1/D19 & 20

This world chart has an appended latitude scale and thus the putative degrees longitudinally can be assessed. The main differences to the QM chart are the addition of Greenland and the removal of the bulk of Northern Russia. Devoid of country names it gives the appearance of being a rushed addition to the Atlas. There is no scale bar with which to assess the map but it is obviously an accurate square map as before.



This world chart is a ‘tour de force’ combining the toponyms of the QM atlas and colouration of the Vienna atlas. It has Greenland and the larger Northern Russian landmass and fortunately a latitude scale. He chart is again undoubtedly square in degrees, but the centre point has been placed slightly east of the other charts but the putative lines indicate a correct alignment. The scale bar is sub-divided into sections having four divisions and is thus 52 units long. But that equals 38 degrees latitudinally or 1.3684 Sbu’s per degree. Given that a degrees is normally 75 Sbu’s (RM) or 90 Miliaria that provides for 65.77 Miliaria per single SBU. But, 65.77 x 38 degrees equals 2500 and it is therefore possible the scale bar is actually 4 x 50 per division and an overall length of 2500 Miliaria.

ChDHa/1/D22 & 23


According to the scale bar appended it appears to be 62 ½ Miliaria per degree and thus in all probability the original size of the World Chart but has lost some accuracy in its draughtsmanship or scale bar.


I have reproduced the three charts as outlines and by equalizing them have produced two overlay diagrams which compare the QM atlas to the Dresden Atlas and then the Dresden Atlas to the Vienna Atlas world chart.
Diogo Homem is therefore obviously carrying forward a pattern/template from London c1588 to Venice in 1568 and thus we can assume the origins of all his works stem from the lost c1545 chart and then the QM atlas which would in all probability have used it for its production. No doubt many pages have been lost in the intervening years.







I cannot detect a cross fertilisation from London to Dieppe, the closest other centre for the cartography of World charts and do not think Diogo Homem was therefore present in France between 1547 and 1555. Where he was is therefore a mystery to be solved in the future.


The following charts are from the same period as the Diogo Homem Atlas charts and may possibly have been available in the ‘lost’ period for Homem. The fact that I cannot detect a similarity does not mean they should be dismissed as they may have produced ideas for Diogo Homem to incorporate that would not be obvious.

1) Girolamo de Verrazzano 1529 Diagram ChDHa/1/D29
2) Jean Mallard, c1540 Diagram ChDHa/1/D30
3) Jean Rotz, 1542 Diagram ChDha/1/D31
4) Guillame Brouscon 1543 Diagram ChDHa/1/D32
5) Pierre Desceliers 1546 Diagram ChDha/1/D33
6) Pierre Desceliers 1550 Diagram ChDha/1/D34
7) lopo Homem 1554 Diagram ChDHa/1/D35
8) Le Testu 1556 Diagram ChDha/1/D36
9) Andreas Homem 1559 Diagram ChDha/1/D37
10) Nicolas Desliens Diagram ChDha/1/D38

Michael J Ferrar November 2021.











Michael J Ferrar November 2021.